I'm still trying to arrange an audition but can give you my opinion. Take it with a grain of salt, I suppose.

I'd say go with the 340. I always say go with the best center you can afford. Your room is pretty small and from what I have read you would probably be quite pleased with the 170... but I'd still go with the 340.

My recommendation is based on home theater, not music listening. If you are buying primarily for music you should definitely ask someone other than me.