Is a sub on a different circuit often a problem?

Michael, yes essentially you are correct, but with an IEC fitting, so you would have fewer connectors vs. an outlet plus PC. But an outlet, done right, is probably the better long term option, if you are sure the need will remain.

Twb2, if I understand you right, you're suggesting that I make myself a long extension cord? I can hard-wire a new outlet close to where the sub will sit with about 2 hours of work chiseling a space in the brick to place the box and then fishing the wire down to the basement. This would definitely be my preferred method of handling it, because it's safer and more aesthetically pleasing (just in case one day I have to consider the WAF).

Bob Reynolds, have you experienced the hum when they weren't on different circuits? I'm just trying to get a sense of the probability that I'll have to deal with this.

Michael

One way to deal with this is to create a custom PC with high quality 10 or 12 gauge wire and quality terminations. I did one (30') from BPT with good results, and at reasonable cost. Then you plug it into your dedicated circuit.

Bob_reynolds is exactly right.