You should be able to fit up to 250 mm cards (460gtx, 5850, 5870, 6850, 6870). 270mm cards (570gtx, 580gtx, 6950, 6970) might be obstructed due to the sata connector on the hard drive. You should be able flip the hard drive upside down so that you can fit 270mm cards.
The PSU has 32A combined...