Relatively speaking there are few prepros that are at the level of a good stereo preamp. While those few are no doubt very good, what are the odds that it would be best for you and your system/tastes? And, IMO, the preamp is one of the most critical components to get right. It just seems very limiting when you could have the whole world of stereo preamps to choose from. And although HT bypass is a nice feature, it is not necessary so your choices in stereo preamps needn't be limited by that either. Maybe you'll get lucky and one of the better prepros may also be right for you, but the odds seem much better going the other route.
The other consideration is you'll likely pay up big for one of the better prepros, and a lot of that expense goes for handling the center/surround channels. Personally, I'd rather put more money into a stereo pre (and amp) and use a decent AVR or prepro to handle surround/processing duties. Not familiar with Yamaha's processing, but the Audessey and Pioneer systems seem to get good feedback. But my priority is 2-channel so YMMV. Hope this helps and best of luck.
The other consideration is you'll likely pay up big for one of the better prepros, and a lot of that expense goes for handling the center/surround channels. Personally, I'd rather put more money into a stereo pre (and amp) and use a decent AVR or prepro to handle surround/processing duties. Not familiar with Yamaha's processing, but the Audessey and Pioneer systems seem to get good feedback. But my priority is 2-channel so YMMV. Hope this helps and best of luck.