Funny you should mention that cbesper, my sub died about two weeks ago, after three months or so of service. They are sending me a box so that I can return it for repair (charging me $40) or replacement since it is under warranty, but I don't think that "refund" is an option. If I were gonna replace mine I think it would be with an RBH 10"er, because they say that it is especially "musical". I think that RBH speakers are something special and their subs are highly regarded and glowingly reviewed.
I don't think that your SVS 12"er is necessarily overkill, it's just important that the frequencies up through 150 - 200 hz integrate nicely with the little Orbs. I thought that the 8" Orb did a good job of that, but wouldn't mind just a tad lower extension. I don't play my sub that loud, as I just want good coverage the low end to the high without emphasis on much more than the voice frequencies. Our room is 28" by 16" with 18' vaulted cieling, but the little Orbs fill it up remarkably well when we crank up a concert DVD or the movie gets loud. My only complaint is with the center channel...that's where I hear a little "hollowness" and miss the deeper resonance of, say something like Sean Connery's voice. I am about to try another CC speaker to see if that makes a difference, but don't have it yet, and want to wait till my sub is returned before making a definitive comparison.
This stuff is sometimes very frustrating, and it makes me a little nervous that the Orb subs seem to have an alarming failure rate...what happens when the warranty period is over?