I too grappled with an economical way of getting double duty from my HT to play music using tubes. Here's what I did on a friend's advice that has worked well for me the past 6 months: source (h/k dvd 22)- tube preamp (tono) - cd-in avr (marantz 7300) - speakers (axioms+svs). Aside from calibrating the volume control in the preamp w/ the avr, set-up required nothing else.
I'm not saying the set-up is the best, but I can vouch for the "improved sound" tubes provide over solid state in my system. Also, all the features in the AVR work. I can choose Dolby, DTS, Multi-Stereo, Stereo over the default Source Direct if I wish. And I get to use the AVR's bass management, a distinct plus if you don't have full-range mains (I have the M22s).
I think this route is a good way to "scale into" tubes. If you're happy with it and want more, you can get the tube amp next.
