The crossovers in most entry/mid-level tower speakers stay in play when bi-amping. There is absolutely nothing wrong with b-amping a nice set of towers with a receiver. I had my B&W seven series bi-amped from a 6000 series Marantz receiver for years they sounded great. it is by no means going to double the sound put or anything near it. But it will absolutely clean things up a bit and increase dynamic range. Of course a better amp will sound better!!! Duh!!! That goes without saying.

Also receivers have had bi-amp options for at least 7-8 years!!!