Continuing on our path to electronic enlightenment this week we'll be taking you through the marketing-hyperbole-ridden world of video cards.

The video card, or GPU (graphics processing unit), is the single biggest factor when it comes to determining the gaming performance of a PC, however it can also be the noisiest, most power hungry and most expensive part of a system, so striking a balance between desire and practicality is a fine art.

It's also possible that you don't even need one in the first place - if you're simply building a home theatre PC or just plain ol' don't play games (what are you doing here at Gameplanet if that is the case though?) then you can probably get away with using a motherboard with decent onboard video. For the rest of us however, a discrete GPU is a must.

There are two major players in the mainstream GPU market, Nvidia (the incumbent corporate giant) and ATI (the underdog and current crowd favourite), and both can provide solutions ranging from under $100 to over $3,000 NZD. To give you an overview of what is available I'll break the entire range down into five separate price categories and talk you through them all, starting from the bottom going up, and point out the cards which are worth checking out along the way.

<$100, Mostly Media/Lite Gaming

This category won't suffice if you want to turn up virtually any graphics setting in virtually any modern game, however it will run The Sims for the missus if that's the extent of your gaming requirements. These cards will also allow you to do things like convert video into formats playable on portable media devices, and play back high definition movies much more efficiently than your CPU can.

Other than being cheap, one advantage of cards in this category is that they don't require a lot of power (mostly under 70w), and thus generally only need small fans to keep them cool (or no fan at all, often) which also means they are very quiet - just what you want in a HTPC or a PC that sits in a living space in your home. Make sure the one you get has an HDMI connection for maximum futureproofedness.

Recommended viewing:
Nvidia GeForce 210
ATI Radeon HD 4650

$100 - $200, Budget Gaming

Here we finally see some cards that can actually deliver quality gaming performance, most notably the Radeon HD 4850 which is one of the most popular video cards of all time. Cards of this calibre will handle most modern games at medium or higher settings at resolutions up to 1920x1080.

Beware of gimmicks like having 1GB of memory on this range of cards - they don't have enough grunt to justify more than 512MB of onboard RAM so it's not worth paying any extra for. More video memory will help you at very high resolutions (1920x1200 and higher) and/or with high levels of AA ("anti-aliasing", a graphics quality setting which gets rid of the jaggies onscreen), but you also need the processing power to back it up, which you just won't get at this price point.

At this level we still see quite low cooling and power requirements (generally under 100w), but it pays to check reviews out first before settling on any particular model just to avoid any especially noisy cards.

My picks:
Nvidia GeForce GTS 250
ATI Radeon HD 4850

$200 - $400, Mainstream Gaming

This is where business starts getting serious and you can find cards that you can really crank the quality settings up with. Currently I use a 512MB Radeon HD 4870, which is on the cheaper end of this group, with a 1920x1200 screen and it does a fine job with most games but starts to struggle once the AA is turned on, so a slightly more powerful card with more than 512MB of memory should be your preference here.

You will also see DX11 cards pop up in this price range. DX11 is the new multimedia specification from Microsoft and currently only ATI have released cards that can support it, so if you want to stay up with the play and be able to use all the graphics features that upcoming games will have then you'll be wanting one of these. Word to the wise though - not many games will have proper DX11 features for the next 6 months or so, so you could always stick with a good DX10 card for now and upgrade next year.

Also here we start to see bigger, noisier fans, and higher power requirements (up to 200w) so that's something to take into consideration, especially if you plan on adding a second card later on for increased performance in an SLI or Crossfire configuration.

Best of the bunch:
Nvidia GeForce GTX 275
ATI Radeon HD 4890 (DX10), or Radeon HD 5770 (DX11)

$400 - $800, Performance Gaming

Now to the big boys. If you're willing to splash the cash out, you are still (usually) getting good return on your investment in this price arena. These puppies will handle pretty much anything you throw at them, in fact if your monitor is less than 1920x1200 and you don't insist on cranking all in-game quality settings to maximum then you're probably wasting your time looking here.

Nvidia's most powerful card, the GTX 295, slips in at the thick end of this price bracket, and it contains not one but two GPUs on a single card. This means it uses almost 300w by itself, but surprisingly it's not ear-piercingly loud. ATI's current flagship, the HD 5870, seems to push out slightly more noise, but uses over 100w less that the Nvidia card.

There are other slightly more economical cards worthy of mention in this category, like the Radeon HD 5850 and GeForce GTX 285, but if you want no-compromise results you should stick to the two mentioned above.

Nvidia GeForce GTX 295
ATI Radeon HD 5870

$800 - $3000, Enthusiast Gaming

Some people define "Enthusiasts" as those having more dollars than sense, and that wouldn't be entirely untrue when it comes to spending thousands on a graphics solution. I say "solution" because any single Nvidia or ATI card (minus a rare exception or two) can be had for under $1,000. Clocking up this sort of bill, then, requires the purchase of two, three, or even four discrete video cards to be run in a multi-GPU setup.

When running multiple Nvidia cards together for increased performance it is called SLI; when running multiple ATI cards together it is referred to as Crossfire. In both instances, you will need a compatible motherboard, and preferably a hefty power supply as you'll need the thick end of a kilowatt to power some of the more demanding solutions.

To the dismay of many wallet-lightened enthusiasts, you don't often get your money's worth in these situations. I've tested a lot of SLI and Crossfire setups over the years, and very generally speaking - at medium resolutions (~1920x1080) the second GPU will give you a 40% boost in performance, the third will give you up to another 20%, and the last GPU will provide less than 10% more performance. In the end, you're paying 4 times as much for less than twice the performance. This is called the cost of diminishing returns (aka about the only thing I remember from fourth form Economics).

If you must:
Nvidia GeForce GTX 295 (two of)
ATI Radeon HD 5870 (three or four of)

Finally - two things you must remember when choosing a video card, it must fit inside your case, and you must have a PSU powerful enough to run it. Haven't chosen a case or PSU yet? Good, because next week we'll be exploring exactly those.