I would agree on the video card. If it doesn't support DX9x, you will miss out on a number of newer games that will flat out not run on pre-DX9. The ram im not so sure about. While a gig is nice, try 512 first. I run only 512 and it seems adequate.
AGP won\'t fit in PCI-E... unless you use a really good hammer. ~Trotter
So my new list should be;
AMD Athlon XP 2600+ processor
Antec Sonata with 380-Watt power supply
Thermaltake Volcano 9
512 crucial ram
ATI 9500 or ATI 9600
IBM Hitachi 80GB Deskstar 120GXP 7200rpm Ultra ATA100
Lite-On 52x/32x/52x CD-RW
hey i recommend if ur cpu is retail it already comes with a fan that was made spesically for it and there should be no need to buy new heatsink. but u got a good buget computer there for the money and what does 600 pounds convert into US dollars.