70C load is pretty normal for an i7 920/930 with the stock heatsink. I have my 930 at 3.0GHz on the stock heatsink and it hovers 70 to 74. I run Folding@Home 24/7 so I only ever see load temps, the i7 is too awesome to waste time idling. I'm not too thrilled with those temps and I'd really like to overclock some more so I plan on buying a better heatsink sometime soon.
I too have the Antec 900, I moved the drive cages up 2 spots so that the front intake fans move air directly over the motherboard rather than wasting it blowing at the PSU. I'm wondering what the best heatsink would be for the 900 or if the H50 is worth it. The problem with the H50 is that you really don't get to take advantage of the top fan, the radiator is designed for a rear 120mm fan.
