I have a Harman Kardon HK3490 Stereo,1 pair of Polk Audio Monitor 50 speakers and a Polk Audio PSW505 subwoofer. I have the speakers connected with a single cable. The speaker manual says the speakers can be bi-wired or bi-amped. Can I run another cable from the stereo's A/B speaker connection as a cheap bi-amp option? Meaning the A side connected to the top terminals of the speaker and the B side connected to the bottom terminals of the speaker with the jumper removed.
You could, but you wouldn't see any benefit to it. If you had a 5 channel receiver, and put it into 5 channel stereo, you could biamp, but that's even questionable if you'd see real benefits. In most cases with entry to mid level amplifiers, you will end up bound by the power supply anyways.