I recently did an install with Bag End Subs.  My only issue with them is that it takes twice as many bag end subs to achieve the dB level that most conventional subs can put out.
 
We put in 16 of the Active S18s.  Probably could have used 32 though for the size of this room.  But it is a good sounding system.

I switch between fingers and a pick (HORRORS!!!), so I need a post EQ feed or my basic sound is going to get real clanky! I suppose the FOH could be alerted to a bass change, but for the most part, we are a ways down the food chain when dialing in each song!
 
Larry