I like a lot of these responses.
I agree that avoiding being negative is a good idea. Two other things. First, demonstrate your system to him using material he is familiar with. Some people don't know what they are missing AND are receptive to new experiences and new ideas (you need both). Second, make it about you and not about him or his stuff. For instance, you could say "I've heard (or owned) Bose speakers; while I think they are great for some people, I have found that the system I have now is very satisfying for me. There is a lot of competition in the home audio/video market, and different people weigh certain attributes differently or perceive products in different ways."
I mean really, Bose is scorned because it seems overpriced relative to its sonic performance. I personally don't think Bose systems sound very good. HOWEVER, some people may justifiably place an ABSOLUTE premium on ease of use and/or speaker size. You cannot fault them for having different priorities. The problem seems to be when a Bose owner thinks he has purchased credibility or status in the eyes of people who have more than a passing interest in how things sound.
The other conversation I sometimes have with folks like this has to do with the science of speaker size. You know, it's a physics problem and size really does matter; there is no magic bullet relative to moving enough air around in your room for a satisfying experience. Bose shifts some of that burden by crossing over to the subwoofer at a relatively high point. TO MY EARS, that is distracting because the sound is more easily localized and seems less spacious. Again, your comments should be all about you and your ears, not him and his system.
I think James' approach is best, though. "Do YOU like it?" puts the judgement where it belongs.
