I have a B&K AVR507, which was the successor to the 307. It's manual never mentions bi-amping, and I'm assuming the 307 also cannot do that. Bi-amping through an AVR receiver is a more recent "fashion trend" that in reality is a dishonest promise. Receiver manufacturers who make such claims are doing a disservice. These B&K receivers were made before that particular type of dishonest marketing came into fashion.
The power output of those receivers are similar, possibly identical, and they are powerful enough to drive all the speakers I've tried. I suspect your Snells are also more than adequately driven by your receiver.
If you don't have jumper wires in place on your speakers, how do you have them wired? One set of black & red terminals drives the tweeters, and the other set drives the woofer. If you connect a short wire between both black terminals, and another between both red terminals, you will drive both from one cable running from your receiver.