advice on a new gaming pc

Im looking for a new gaming rig would appreciate any help

thanx in advance

budget is £350 - £400

quad core or core 2 duo (not really fussed)

minimum 500gb hard drive

3gb ram

gfx card is very important i need a decent one

also is it best to go for a amd or intel nividia or ati gfx

very likely will be getting a hd monitor for this machine.

Can't advise on the whole gaming rig specs but off the top of me' head and considering ur budgetu should get an ATI gpu for the best price/performance, perhaps in the 48xx-series...