If you're using standard 5.1 or 7.1 decoding, you will lose the .1 part if you don't have a dedicated sub. Any decent processor will allow you to route the .1 to the mains if you like, but that's their processing then, rather than specifically what is recorded. It likely would sound just fine - all I'm suggesting is that a sub is required by the 5.1 and 7.1 spec in their straight form.
I'd always use a matched center for HT. Certainly, unmatched is serviceable if budget prohibits, etc., but I wouldn't be any more inclined to accept an unmatched center for HT than I would be to use mis-matched L/R for stereo music.
I'd always use a matched center for HT. Certainly, unmatched is serviceable if budget prohibits, etc., but I wouldn't be any more inclined to accept an unmatched center for HT than I would be to use mis-matched L/R for stereo music.