Home theater and 2 channel setup from same speakers?

Yes, it is MUCH easier than most people think. And it is NOT a compromise of yoru 2 channel sound. HT Bypass as people have mentioned is the official name for it.

What it really is, is a seperate input to recieve pre-out from your HT reciever for the front 2 speakers. So when you want to watch a movie, you just switch inputs.

What isn’t often made is an amp (not integrated) with 2 inputs. That is what I have. My tube amp is an integrated but I bypass the volume to make it an amp and use the multiple inputs--one for my preamp, and one for my HT amp.  I am having a custom amp built, and one feature I've ordered is multiple inputs.

Jerry

PS You do need an HT amp that has PRE OUT, at least for the 2 front channels. Of course once you hook it up this way you’ll go into the HT setup and balance the speakers in this mode.

I do something similar, but not with amps.  The DAC3 from Benchmark has home theater bypass and multiple inputs - some analog and some digital.  My streamer connects to the digital DAC input and my preamp outs of my receiver connects to the analog inputs of the dac.  Essentially, The dac acts as a pre-amp with volume control and muiltipe inputs.  It even has multiple analog outputs so I can connect a couple subs.  Works great, but only 1 amp powering the front speakers for 2 channel and for HT.    

One other consideration, if choosing a tube preamp, is whether the home theater bypass functions even when the preamp is powered off.  Most don't have that feature, but some do, thereby extending tube (and possibly other circuit components) life.

@sleepysurf  ^good point^  (That is exactly how mine works.)

...  The room I'm in could probably support both sets of L/R speakers but I was curious if I wanted to downsize speakers, is it possible to run a AVR and tube integrated amp without physically moving cables and such?

i would demo the new L/R speakers first to make sure that they are voiced in a way that is compatible with your existing 5.1 speakers (or the remaining 3,1 part).

it is possible that the crossover, and phase, could put a null where you want sound… particularly the center channel and the new front L/R.

9I started with 2.1, so I just went out and got used center and surrounds by the same manufacturer to avoid the issue.)

What are your existing 5,1 speakers?