I believe that you get value from bi-amping speakers that are designed to be bi-amped and have a proper complimentary crossover- preferably made by the speaker manufacturer for that particular set of speakers.
Because there are so many variables in "complex" amplification I'd start by listening to the above before you buy.
I recently bought a set of Bryston Model Ts. I listened to them bi-amped with a matching crossover. They sounded wonderful. When I got them home my ARC VT130 couldn't keep up with the speaker's demands at higher volume and the bass was a bit mushier than when they were bi-amped. I bought Bryston's crossover and a pair of their solid state 7B's to drive the woofers and I drive the mids/tweets with my ARC tube amp. Viola! They sounded as good (actually a little better thanks to the tube amp) as they did in the retailer's listening room.
Moral of the story: Listen before you buy and be prepared to spend a lot more money than you hoped to get it just right. I've got my wife and car up for sale now to recover the added costs of bi-amping.