You can really use ANY preamp, and simply use the tape input or auxilary input, etc. I've used the Audio Research 15 and 16 (with bypass) and, with the right tube compliments, these preamps are about in the same ball park. The 16 getting the edge with it's more pure inputs.
still, i'd get the best preamp you can get your hands on for 2 channel use, and simply accept connecting the AV pre/pro through any good (or best, whatever) input on the 2 channnel pre. HT will still sound great, and the 2 channel will be excellent. This is not that big of a deal. I've used my 5.1 pre's into several higher end 2 channel analog preamp's, and never a problem!
still, i'd get the best preamp you can get your hands on for 2 channel use, and simply accept connecting the AV pre/pro through any good (or best, whatever) input on the 2 channnel pre. HT will still sound great, and the 2 channel will be excellent. This is not that big of a deal. I've used my 5.1 pre's into several higher end 2 channel analog preamp's, and never a problem!