Cross-platform games aren't getting any less demanding with time. If DiRT 2 with its DirectX 11 capabilities isn't evidence enough, then take a gander at the recommended system specifications for DICE's upcoming Battlefield: Bad Company 2 and Battlefield 1943, as relayed by Shacknews.
The minimum requirements look innocuous enough—2GHz Core 2 Duo, high-end DirectX 9 graphics, and Windows XP—but the recommended specs really kick things up a notch. DICE says you'll want a quad-core processor, a GeForce GTX 260 graphics card, and either Windows Vista or Windows 7. (Oddly, though, you'll purportedly get by fine with 2GB of RAM.) The games will also take up 10-15GB on your hard drive, although disc-based copies will have smaller footprints.
Both titles will be based on the same engine, Frostbite, which explains the shared requirements. We recently learned that Battlefield: Bad Company 2 will feature DirectX 11 support, however, so a Radeon HD 5000-series card might be your best bet for that game (assuming you can actually find one, that is).
Shacknews says Bad Company 2 will arrive on March 2 for the PC, Xbox 360, and PlayStation 3. Battlefield 1943 is already out on consoles, but the PC version isn't due until the first quarter of next year.