In this guide I will explain what a graphics card is and reccomend the best in several price bracketsWhat is a Graphics Card?
A graphics card or video card is an additional board than can be purchased or come with a computer. It consists of a graphic processing unit that deals with all graphics rendering and video memory to hold data for easy acesss. They come in many varieties, PCI, AGP, PCI-e x16 and now PCI-e x16 2.0. The most common is now PCI-e x16 2.0
This is now the standard interface that graphics cards use in computers.
PCI-Express 2.0 graphics cards are backwards compatible with motherboards featuring earlier 1.1 slots
PCI-Express is not backwards compatible with PCI.
PCI-Express will supply 75W via the motherboard slot. Higher power cards will require a dedicated 6pin or 8pin PCI-E power cable from the PSU.
An ATi card will work on both Intel and AMD motherboards. An nVidia card will work on both Intel and AMD motherboards.
What is the best graphics card?
As of 12/07/2008, the best single card you can purchase is an nVidia GTX280 which will set you back around £350/$500, which to be honest is alot of money for something that yields only a small amount more performance than both the nVidia 9800GX2 which is £50/$100 less or an ATi HD4870 for £100/$200 less.
In terms of price vs performance ratio however, the new ATi Raedon 4850 comes out on top, costing only £120/$190 and keeping up with the new GTX 260 from nVidia. The 4850's bigger brother - the 4870 - keeps up with the 9800GX2, and most of the time challenging the GTX 280 for much less!
So in answer to the question, for ultimate performance with no budget; the nVidia GTX 280 1GB and for budget with high performance in mind; the ATi 4850 512MB.
What is SLi / Crossfire?
SLi and Crossfire are technologies from nVidia and ATi respectively, they allow you use upto four graphics cards on a supporting motherboard for ultimate performace. This doesn't always apply however, and only small performance gains are seen at resolutions of around 1280 x 1024. If you are running 1920 x 1200 then you will see a larger performance increase.
I'd reccomend trying to get the best single card solution you can and then upgrading, as most probably by the time you come to add another card, they're will be a better single card on the market!
(note: SLi is only available on nVidia chipset motherboards & Crossfire is available on both AMD and Intel chipset motherboards)