What components do you have in your system now? What is HT and what is 2-channel?
I don't currently have an HT system. However, several times in the past I had combined HT/2-channel systems and they worked well. If configured correctly, the HT setup has zero effect on 2-channel sound quality and actually the HT components don't even need to be turned-on when playing 2-channel music.
If I were looking to do a combo HT/2-Channel system today, I would have to look at the Backert Labs Rhumba 1.3 pre-amp. It is a tube-based pre-amp. One feature I really like about it is that it has HT bypass that is activated when the pre-amp is powered off. So, no tube wear when listening to HT.