I'm afraid I can't quite throw in an X1900XT, they have gone up in price a little recently but this ought to be suitable, the X1800XT will run everything you want with no problems whatsoever and it is under budget, have a couple of drinks on me

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CA-040-AN Antec Sonata II Piano Black Quiet Case - 450W Smart Power PSU (CA-040-AN)
£59.95 £59.95
MB-088-AS Asus A8N-E nForce4 Ultra (Socket 939) PCI-Express Motherboard (MB-088-AS)
£59.95 £59.95
MY-046-GL GeIL 2GB (2x1GB) PC3200 Value Dual Channel Kit CAS3 (GE2GB3200BDC) (MY-046-GL)
£94.95 £94.95
HD-046-WD Western Digital Caviar SE16 250GB 2500KS SATA-II 16MB Cache - OEM (HD-046-WD)
£55.95 £55.95
CD-026-NE NEC ND4551 16x16 DVD±RW Dual Layer LabelFlash ReWriter (Black) - OEM (CD-026-NE)
£25.95 £25.95
CP-134-AM AMD Athlon 64 X2 Dual Core 3800+ (Socket 939) - Retail (ADA3800BVBOX) (CP-134-AM)
£175.95 £175.95
GX-048-PC PowerColor ATI Radeon X1800 XT 512MB GDDR3 AVIVO TV-Out/Dual DVI (PCI-Express) - Retail (GX-048-PC)
£199.95 £199.95
Subtotal £672.65
VAT £117.72
Total £790.37