Geoff, First I think Aperion makes the best sub (pun intended) 12" sub on the market. For music the 8" will be great, for hometheater it will be sufficient but the 10" is a big step up, much more so than moving from 10" to 12".
Quanah, the Aperion 10" is a marvelous piece. Read the review at
www.cheaphometheater.com. It really compares well to many expensive 12" subs, except for the low end extension. I don't think you'll be disappointed.
I upgraded from the 10" to the 12" and loaned the 10" to my friend. However, he's moving soon so I might be putting mine up for sale.
I think Aperion makes incredible speakers. More people should check them out.