I also own a pair of ANC7. I have tried the Denon NC732. AVOID those. They were just awful. Haven't tried the Denon NC800, but I would wait for a very favorable review before bothering with them. Likewise avoid the Bose QC3. Simply not as good as the ANC7.
The QC15 are much better than the QC3, but I would never recommend they be someone's only pair of headphones. They have bass boom issues and they can distort pretty heavily (from the pair I tried, at least). I'm talking actual clipping. I thought they had their advantages over the ANC7, but not nearly enough to justify the price, and I would never recommend them over the ANC7 as a day-to-day pair.
I haven't yet heard the Sennheiser ANC line. Some people seem to like them for what they are, but I wouldn't necessarily expect them to be any better than your Audio Technicas.
If you're looking for an upgrade in sound but can't go with something short of an NC headphone, I think you need to start looking into IEMs.