Need helping choosing a new system as I am a noob

I have only recently become interested in computers (hardware) because of gaming  , Ihave 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, I am on a tight budget (£350 max for unit alone) as I am a student. I have been ooking at these 2 systems:

http://www.pcworld.co.uk/martprd/store/pcw_page.jsp?BV_...

and

http://www.pcworld.co.uk/martprd/store/pcw_page.jsp?BV_...

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. I will be using my pc mainly for gaming so I will upgrade the graphic card, ati hd 3870 or nvidia 880 gt. I am open to any suggestions for anything.
thanks