do yer preamps have a tape loop? if so, have yer audio preamp hooked-up full-time *only* to the two main audio speakers/amps. listen to music as always. then, for movies, have yer h-t preamps' main outs feed *only* the center & surround channel amps. for the two *front* h-t channels, feed the tape outs of yer h-t preamp into the tape ins of the audio preamp. when watching movies, set the audio preamp to the *tape* source. you will need to adjust volume for the main channels (audio preamp) & the center/surrounds (h-t preamp) separately, but ewe shouldn't have to do any more plugging-unplugging.
of course, ewe could get an audio preamp that has a true processor default-loop. hooked up as described, (except your h-t preamp feeds the audio preamps' processor loop instead of its tape loop), the h-t preamp will control the wolume of the speakers hooked up to the audio preamp, as well as the center/surround speakers...
confused yet? ;~) good luck, doug s.