Best way to go HT with focus on 2 channel

I've had the same experience as S23chang. Moving the stereo speakers or even placing a video screen between them to accommodate Home Theater lets the stereo image fall apart. You seem to have some very nice two channel gear. Have you ever had your two channel setup, room, speaker placement, etc. evaluated? Once dialed in even minor changes will dramatically effect the stereo presentation.

I gave up and went an inexpensive HT setup in another room. The 5.1 audio (not HT) is another animal.

Thanks for all the great advice! I was out of town for a while and am thrilled with all the great responses. A couple more questions:

If I were to use one of these configurations, what is the best way to connect a powered sub for use in 2 channel and HT?

If I use an HT pre/processor and go with a separate amp for the rear speakers do I need to match power or gain of my 2 channel amp?

Theta surround processor with possibility to connect external GENVIII DAC/preamp.

I grafted on an HT setup to my 2-channel rig as well, pretty much the same way others have mentioned here. I have my pure 2-channel setup with my sources (arcam FMJ CD23 and a VPI HW-19Jr turntable) going directly into my preamp (audible illusions mod 3) which drives the 2 main channels. I use a cheapie Harmon Kardon refurb processor (AV230) as a surround processor; at the time, this was the cheapest receiver they sold with preouts on all channels. I feed my HT sources (LD player, cheapie Sony DVD/SACD, Windows media center PC, laptop, occasional Xbox) into the surround receiver. L and R preouts from the surround receiver go the preamp onto an unused input. Had to pick a volume setting on the preamp that was close to full volume and calibrate the channels on the surround receiver at that volume level and then always have to return to that volume level when running in surround mode.

I am also able to run SACD in surround or 3-channel mode (e.g. living stereo releases) for music, but it's not as purely direct as it could be since the L and R channels from my SACD/DVD go all into the surround receiver. Theoretically, I would feed the L + R directly from the SACD into my preamp as well, but I'd need to deal with coordinating volume levels between both systems.

regarding your sub question, personally, I only use my sub for HT duty as the LFE channel and not in 2-channel at all. A couple times, I have hooked up the sub for 2-channel use in parallel with the L and R channels (so did not use the line level crossover in the sub) by using another setup of outputs on my preamp.

Last thought is that since you are running a tube amp, you'll obviously also be using these amps to drive L + R channels for all HT duty as well so you'll shorten the life on them. Today, I'm running solid state amp, but my intent was to also move to VTL amps and preamps and I have that same concern.

Your setup must be very nice sounding. Looks like you've done a great job building a musical system. I think you're thinking the right thing by keeping your 2-channel setup as pure as possible and tacking on the HT onto that.

A lot above, like switching the pre/pro through your 2channel pre, will work fine. That's how I've done it in the past, and it's perfect. And you WILL NEED an outboard pre/pro..don't use the multichannel out's of you're dvd for dD/DTS processing. It's not as good.
Your challenge would be the matching speaker for your center and rears to go with the mains. Tonally, they need to be identical to do it right. If not, forget it. I'd stay 2 channel with a sub! Otherwise, get 5/6/7 matching small satalites around the room for movies, and swich to 2 channel and your main speakers for music. Otherwise, you'll have a very cruddy and compromised system with "mismatched speakers"...garanteed! I say no no no on that idea.
The other choice is to do quality speakers all around, matching, and ditch your existing 2 channel speakers, if you can't get matching center and rears.