I'd want the graphics to be medium - high settings, basically, and for the computer itself to be reasonably priced (£400 - £600). Although it may disappoint certain people, I do not have the time or interest (sorry to disappoint, it's just not my thing) to build a computer myself, so I'd appreciate advice from people who have the passion and knowledge.
The mentioned game, a military simulator, is the one I'll likely play most extensively and I shouldn't need to over-complicate my purchase. Any advice, please? If you're to recommend a certain site, I'd be thankful if it wasn't relatively unknown and/or lacking any substantial coverage in media.