Well, if you have the room, it is the way to go - keep the amp away from the direct vibrations of the sub - should assist with longevity.
I use a BASH SAM300 unit, from this Canadian company, and have for about 2 years now.
http://www.bashaudio.com/samunits.htmIt is great, BUT I have little to compare it to. It is the first sub amp I have owned, outside of a great little Yamaha YST sub I owned for a while, with a built in amp.
I bought the BASH unit locally, but they mostly cater to the OEM market, so it took a little chatting.
Fast, well controlled bass, with both my DIY subs. Money well spent.
Mark in Canada