You should have no bottlenecking issues, maybe a light overclock would help, but you should be fine. As for the power supply, all you need is a good quality 750w, and I mean GOOD QUALITY. Even an average 1100w is not recommended. Get one of these:
Also why the GTX 295? The 5870 is basically just as fast, has DX11, and is a single card system so won't be an issue in the future (SLI/cfx tends to be problematic). Oh its also a lot cheaper... Hell for a bit more you could get a 5970, which destroys a GTX 295.