That Corsair 750W PSU is perfectly suitable for a GTX 470 or 480. SLI might be kinda close on the power budget though. But you could probably crossfire ATI 5850's without a hitch on that PSU.
The GTX 470 (reference design/cooler) run about 94/95C at 100% load. I can personally attest to that.
If you have a small room, or don't have good A/C in your home, it's going to make the room pretty warm.
The GTX 470 will out perform a standard ATI 5850. However it will use more power, and is hotter. Because it runs so hot, the cooler runs at high speeds while gaming, and can become loud depending on how close you sit to your PC. My PC sits right beside me, with the side vent on the case pointing the noise right at my ear. I just turn my speakers up louder >:)