I have been seriously considering the 20's but have just been really worried about timbre matching since the idea is to finish my theater with these speakers. Well atleast for the next 3 or so years. BTW I do have a sub and just failed to mention it, it is a B&W ASW 600. I guess my question is, is it really worth getting the 20's and not matching versus having 9's that will match?
That's a tough one. Would your dealer allow you to try a pair at home, so that you can listen for yourself? Then you can decide if there will be an issue with timbre matching. If you've decided that you will be purchasing one of these pairs of speakers, he may have no problem with it, since he knows he will be getting a sale out of it.
OTOH, you may want to look at it this way. Going to Monitor 9's from the Titans won't give you much, if any, improvement in sound quality. They're from the same line, using the same drivers and probably the same crossover components About all you will gain is deeper bass extension. And, if you already have a subwoofer and don't run your mains set to 'large' on the AVR, you get virtually nothing for your investment.
With the Studio 20's however, there is a definite improvement in sound and build quality. That would be a worthwhile investment, if you want to upgrade your system.
To sum up, I'd say try to get a loaner pair of 20's, try them at home and decide if timbre matching is going to be a problem. If it isn't a problem, you're all set! If they don't match well and you have no intention of upgrading your centre speaker, I would stick with the Titans and maybe think about an earth-shaking sub instead!
Good luck!