Best way to go HT with focus on 2 channel

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 personally agree about the movies, and that's that the picture is first priority for the experience. Still, as an adiophile first, quality of sound has to be there, but it's second for the experience.
I would still rather have quality over quantity, and don't care about sitting between two speakers anymore. I'd rather "share" the experience with other seats in the house. That said, the multichannel system is the best regardless for me personally. Getting 5/6 or more speakers tuned in harmony of high quality sound is just fine by me...I don't need a two channel "sit in the middle" set up anymore. I'm over that...got people to let in the house now...bye