If you are looking at multichannel (as in surround sound) I've almost never heard of someone going tube. Martin Logan speakers are power hungry and all things being equal they GREATLY benefit from extra power. The only exception would be if you are interestened in a super, super high-end mutichannel system for music and you had a HUGE budget. High powered tube amps are extremely expensive and 5 channels would create lots of heat too.

Speakers dictate the choice of amp. I agree with Jackfish. Martin Logans require a lot of power, so unless you have a very substantial budget that would allow you to purchase a very high power tube amp, you will be limited to Solid State, which in and of itself is not a problem.

As far as preamps are concerned, I'm partial to tube preamps. I can't categorically say that tube preamps are better across the board, but I find that I like the quality that tube preamps bring and I also find that it's easier to find a good tube pre on a budget than a good solid state.

Buy tubes anf forget the silly surround fad. You will get better sound. If you are in it for the video, buy solid state.

I think it's been suggested to look into Audiogon, eBay, or other sources of pre-owned stuff. You might get a good pre-amp there too.

If you ever get back into tubes, one possible way is a reasonably powered amp with say 10-50 watts but powering very efficient speakers. The selection of available speakers like this are pretty narrow. Good luck with your search.