Help choosing new system based on the CPU

I have a pretty old computer and it's not holding up too well with newer games (it's from 2002 lol, 2.0GHz intel P4, 768mb sd ram and 128mb ATI 1300 pro). So I'm now after a new system, mainly for gaming, I am on a tight budget (£350 max for unit alone) as I am a student. I have put this post in the "CPU" section because I am trying to decide what system to buy based on the CPU. I have been out of computer the computer world for 2 years now so I don't anything as everything as changed (AMD was best for gaming when I left). I Have been looking at these 2 systems:

http://www.pcworld.co.uk/martprd/s [...] egory_oid=

(Packard Bell with AMD Phenom 9500, 2 gb ram, 250 GB hard drive, Windows Vista @ £320)

and

http://www.pcworld.co.uk/martprd/s [...] oid=-28485

(Packard Bell with Intel E4500 2 duo, 2 gb ram, 360 GB hard drive, Windows Vista @ £220)

So far I'm leaning more towards the IMEDIA 2423 with the amd 9500 quad core, because it seems like a good price for a quad but I heard the other system with the intel e4500 duo can overclock like heck. Like I said I will be using my pc mainly for gaming so I will upgrade the graphic card, ati hd 3870 or nvidia 880 gt. Anyone feel free to suggest anything. Thanks