You can't "bridge" these amps. You can send them back to B&K and they can convert them to MONO amps. You could use one channel of one amp on one speaker, but it won't change the power rating. If your speakers are bi-wireable, you could run them in vertical bi-amp setup, but again no power increase. These will be able to handle the Infinity SM122's in whatever configuration you use.
I have two B&K ST 140s that I'd like to bridge
I would like to connect each (I have two) of these amps to a separate speaker. The speakers are Infinity Reference SM 122s. I'm not sure what their impedance is. Will this work acceptably for both the amps and speakers? Will the impedance be a problem? I've heard that the ST's don't like to drive a 4 ohm load. Is that what I would have?