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!