I have it at 2.96 (8x347 or something around there), with an Arctic Cooling Freezer 7 Pro. HOw far could I take safely, and what is actually practical to take it to?
That's hard to say since all cpus OC differently. I imagine you could take it to 3.6Ghz with the right cooling. With what you have, probably 3.15Ghz-3.40Ghz.
I had my e6750 running at 3.4 (8 x 425) with no voltage increase and just a stock HSF. I just added a Freezer 7 Pro tonight and am going to take it to 3.6, which is very doable on air cooling.