I agree for big Bing/Bang/Boom movies. However, here's my problem for most music. When you use a sub, you define/set your crossover. In a full range speaker, the speaker designer defines and executes the crossover. Somehow, I don't think my subjectively determined crossover point, or my AVR's crossover execution can possibly be as good as that of somebody like Dennis Murphy.
ImcLoud, when I was shopping for new speakers, you recommended Phil3s ahead of several much more expensive speakers. I went with the Phil3s. I consider them "affordable". I have 2 very strong subs. But most of my music listening is done in stereo w/o the subs. True, I get more bass w/ the subs, but I feel I get better bass w/ just the Phil3s.
So while I would absolutely recommend a sub or 2 for any HT system, I would not necessarily recommend using them for most music. It depends entirely on your Front L/R speakers, and they don't have to cost $120k.