I have few pair of JBL cs3115's (not Pi's as yet!)
Im using a Peavey active crossover http://www.peavey.com/processors/xd234.html
you cant beat a Behringer for the money, and Rane is great stuff though i dont own any. I have read about guys running SS to the bottom and tubes to the top. I'd like to try this myself sometime but I dont have any tube gear yet. "they say" It takes the harshness of the compression drivers and still gives some meat to the bottom.
If you want volume and thunder. I cant come close with passive to what biamp can do. I run 550wpc to the bottom, 300wpc to the mid and 100wpc to the top in a triamp. I was just as happy with biamp and running the mid and top together, and will probably go back to that shortly. for a preamp i use a Mackie mixing board. this is pretty dry and i dont car for it. have to use a BBE sonic, eq, etc. too many things to play with just to listen to a cd. Now I run a CD player direct into the active crossover and this sounds great. plenty of volume.

I have another pair with a passive xo running on 110wpc receiver. this plays pretty stinkin loud and honestly as loud as i need it.
This also sounds better, quality wise. much better presence and i feel like there is a band in front of me.

I dont have the greatest gear for my biamp/active setup so that my be why the Denon sounds better. BUT, If you want to really feel the bass spl, rattle your windows and stress your structure. Biamp is king.
there's no substitute for cubic inches!

Bill