[mattr]

Might be worth printing the minimum spec of and going into a PC shop (even somewhere like PC world) just to get a feel of what you are actually looking for.

Then buy it from someone who knows what they are talking about.

Or have a chat with your colleague from work, he might be able to show you how to build your own for the price of a bottle of decent whisky. Which will get you precisely what you want for much less than you can buy a complete one for (it'll save you more than the cost of a bottle of whisky!)
(You may well find a couple of guys at the car club are into this as well. I know i have probably a dozen or so colleagues/friends/etc who build their own. It's not actually that hard, just a matter of making sure its all compatible.)