Either should handle the games basically although at what detail levels I'm not 100% sure however I would pick the 430w case and I'd stick with the Hitachi over the Maxtor as Maxtor have had a few reliability problems recently although they are not all bad. I don't know if you need the DVI cable or not, maybe worth checking with OcUK as it saves a fair bit of money and you could then perhaps upgrade the graphics card. The below system should be a better overall system since you have got a copy of Vista already.
Intel Core 2 Duo E4300 "LGA775 Allendale" 1.80GHz (800FSB) - Retail £65.99
(£77.54) £65.99
(£77.54)
Sapphire ATI Radeon X1950 Pro 256MB GDDR3 HDTV/Dual DVI (PCI-Express) - Retail £84.99
(£99.86) £84.99
(£99.86)
Seagate Barracuda 7200.10 200GB ST3200820AS SATA-II 8MB Cache - OEM £37.99
(£44.64) £37.99
(£44.64)
Logitech S500 5.1 Black/Silver Surround Speakers - OEM £23.99
(£28.19) £23.99
(£28.19)
OcUK Value Hanns-G HW191D 19" Widescreen LCD Monitor - Silver £91.99
(£108.09) £91.99
(£108.09)
Logitech S96 PS/2 Optical Wheel Mouse Black - OEM £4.49
(£5.28) £4.49
(£5.28)
Logitech Deluxe Keyboard (Black) - OEM £5.49
(£6.45) £5.49
(£6.45)
Antec NSK6500 Super Midi Tower Case - 430W PSU £58.99
(£69.31) £58.99
(£69.31)
LiteON DH-20A1P-45C 20x DVD±RW x12 Ram Dual Layer DVD-Writer (Black) - OEM £14.50
(£17.04) £14.50
(£17.04)
Corsair 2GB DDR2 XMS2-5400C4 TwinX (2x1GB) £47.99
(£56.39) £47.99
(£56.39)
Gigabyte GA_965P_S3 (Socket 775) PCI-Express DDR2 Motherboard £59.99
(£70.49) £59.99
(£70.49)
Sub Total : £496.40
Shipping cost assumes delivery to UK Mainland with:
City Link Parcel Next Day (Delivered Mon-Fri)
(This can be changed during checkout) Shipping : £14.95
Vat : £89.49
Total : £600.84
//edit if you want to game then you will probably need to spend almost all of the £600. The AM2 system isn't inherantly bad but Core2Duo is better.