Johnny,
The only problem you will need to solve is the speaker connections. You should not connect your speakers to two separate amps.
1) You could use bananas for both speaker cable runs and swap them at the speaker connections depending on when you listen to HT or 2-channel
2) Use a speaker switch box. I looked into this a few years ago and came to the conclusion that I would be sacrificing sound quality by connecting my wonderful cables and equipment to this crappy switch. Something may have emerged over the last few years that is audiophile quality, but I doubt it. Worth a look nonetheless.
There are really no other options that come to my mind. I used to have to pull double duty, but my solution was this:
Oppo UDP-205 (played DVD/Blu-Ray and processed surround sound from sources like cable box, Roku) pre-outs
to
Decware Ultra Pre-amp (key component to make all of this work) then connects to the following amps:
- Decware Rachel (center channel)
- Decware Zen Triode (Rears)
The key here is the Decware Ultra 6 channel preamp which was designed to do exactly what you want to do. You can connect your NAD and a Blu-Ray player to the Ultra, as well as other sources that are controlled by the input switch on the Ultra. This way you have one amplifier connected to your front main speakers that can pull double duty (2-channel and HT) without the hassle of two speaker cable sets and having to switch the connections every time. Steve can "mod" the Ultra with caps that would favor 2-channel as opposed to stock, which favors digital sources that need some "help."
You can have an all-tube 2-channel AND HT amplification system. That is what I did and the sound was UNBELIEVABLE for both 2 channel and HT listening.
However, it will require some gear changes. The Ultra would replace the CSP3. You would need to get rid of your 5-channel amp and purchase two amps to power your center channel and rears. Or, use the 5-channel for your rears and just buy one additional amp for your center channel.
Hopefully this helps. May not be ideal for what you were looking to do, but I lived and breathed your very situation and from a SQ perspective, you cannot do better than this configuration with the Ultra at the heart of the system.