I'd got with the IC7 if you don't care about spending 20 more bucks. It'll overclock much better.
Well, maybe not MUCH better, but you will get better performance. In addition, I've had some bad experiences with the IS7. This is just peronal experience, but I've bought an IS7 and an IS7-E, 5 months apart from each other, both from newegg, and both board came damaged. The box was scuffed up, and it looked like the board was just thrown into the box. The IS7-E's northbridge cooler was hanging off.
I don't know. But you get what you pay for. That's what I always say.