New computer for Cataclysm

[Haleth]

Hi all.

I'm looking to buy a new computer for Cataclysm. I love my iMac, but for graphics it just doesn't do the job. The bad graphics card (ATI Radeon HD 2400 XT) and the fact that Windows still has better gaming performance over Mac - not to mention that a good Windows is way cheaper than a good Mac - made me decide that.

I'm clueless about computer hardware though. Where does one buy a good computer, cheap? I hear about people using $800 computers and getting amazing gaming performance. Do they assemble the parts by themselves or is there simply a good brand for gaming?

I'd like to play Cataclysm on Ultra - this means liquid detail, shadows, sunshafts etc all maxed out.

I don't have a specific budget in mind but the cheaper, the better of course (provided there is still quality).

Does anyone have any recommendations about specs, or where I should buy one?

I live in Belgium if that's of any help.