If you really don't want to go for Core2Duo then this is quite a bit under the budget which means you could up the CPU to a 4600 or above very easily and possibly also go for some aftermarket cooling.
BenQ FP202W 20" Widescreen LCD Monitor - Black £139.99
(£164.49) £139.99
(£164.49)
GeIL 2GB (2x1GB) PC6400C4 800MHz Ultra Low Latency DDR2 Dual Channel Kit (GX22GB6400UDC) £49.99
(£58.74) £49.99
(£58.74)
Asus M2N-SLi Deluxe (Socket AM2) PCI-Express DDR2 Motherboard £64.99
(£76.36) £64.99
(£76.36)
AMD Athlon 64 X2 Dual Core 4200+ 2.20GHz (Socket AM2) - Retail £59.99
(£70.49) £59.99
(£70.49)
Logitech Cordless Desktop EX-110 - Retail £17.99
(£21.14) £17.99
(£21.14)
Western Digital Caviar SE16 320GB 3200AAKS SATA-II 16MB Cache - OEM £48.99
(£57.56) £48.99
(£57.56)
Samsung SH-183LBEBN 18x18 DVD±RW Dual Layer Serial ATA Lightscribe ReWriter (Black) - OEM £16.99
(£19.96) £16.99
(£19.96)
Antec NSK6500 Super Midi Tower Case - 430W PSU £58.99
(£69.31) £58.99
(£69.31)
Sub Total : £457.92
Shipping cost assumes delivery to UK Mainland with:
City Link Parcel Next Day (Delivered Mon-Fri)
(This can be changed during checkout) Shipping : £12.95
Vat : £82.40
Total : £553.27