Best way to go HT with focus on 2 channel

I am looking to build my first home theater system, which will have double duty with my 2 channel rig. I really want the focus of quality to be on 2 channel, but want to set up a modest HT rig with 5.1 sound and a plasma. I have a tube pre and amp today and would prefer to keep them in the chain, or move to a tube integrated, maybe a VAC Avatar.

Since I'm new to the HT world, I'm not sure the best way to integrate a AV processor and what exactly I'll need. A little advice from you goners would be a big help. Thanks!
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.
I thought for the longest time to do two systems was the best idea ... no compromises. With my heart fully ensconsed in two channel but desiring a multichannel system, the process began. having accomplished obtaining both, I'm no longer desirous of committing the funds necessary to having both systems... with equal levels of quality... So I personally think compromise seems the way to go, unless of course copius amounts of money are avaiable.

what I've finally decided to do is add a three ch. amp, the same brand center speaker, likewise rear speakers perhaps. (rear speakers are no where near as important in terms of matching as the center is... trust me here...), and of course a full range sub.

If I didn't have the gear I already do and wwere out to go from the jump... I'd agree with the earlier posts... simply add a HT Receiver and the appropriate center and rear spkrs... and a dynamic sub... and not a great amount of money needs be spent to do that either... you'll gain the experience of the surround listening factor, and the grins too. What level of 'experience' you want will determine the money you[ll spend...

So far as I'm concerned, a good two channel set up and a sub are fine for movies.... and in HT the 'BIG DEAL' truly is the screen... spend all you want on sound... but without that big old screen up there to get the true impact of the "theater" you are selling yourself short.

The screen is the ticket. No one goes to listen to a movie.. right? ..for myself this works... Spend the money on improving the two ch. sys. get as big a screen as you can... do the other three ch comfortably.... and don't worry about the overuse of the tubes.... just how long is a movie anyway these days...? Good luck...
The best way to do a music first home theater is to use an anologue 5.1 preamp without any processing. They are the Macintosh, MacCormack Map-1, and Audio Refinement Pre-5. These are high quality 2 channel preamps with 5.1 channel pass through that uses the volume control to control the master volume.

To make this system works you will use a high quality DVD source or universal player that has 5.1 anologue outputs with internal processing (dolby digital, DTS, etc). You will NOT use the digital outputs of your source. The source also has to have bass management (most do) to control the output gain to your speakers in the menu so that you can balance al your speakers. Use a radio shack SPL meter to balance your speakers.

You can then use your tube power amp for your L+R channel and a high quality 3 channel amp for your C+RR+LR. The truth is you can skip your center channel and use full tube for your rears as well if your front speakers image well with a good soundstage. You will go into your sources menu and turn off the center channel. When it processes the multi channel music or movie it will send the center channel info to your L+R channels.

You can have your cake and eat it too.