Let me add some confusion to this discussion.
Actually, I disagree in general with the first response, but agree with some of his specific points.
Just for shits and giggles I tried different cables from my 2-channel system in my HT system's sub. Specifically I hijacked the Acoustic Zen Matrix II, Acoustic Zen Silver Ref II and Audience AU24 to test with my HT sub. In this test the AZ Silver Ref definitely passed a tighter, firmer bass than the other two copper cables and this was with a signal of 100Hz down.
I did this goofy experiment only out of boredom. Like others here I preferred using Analysis Plus Solo and did all the adjustments with sub placement and crossover slope shaping. I found this to be the best way for me.
I also agree with the initial respondent that if substituted in a full range set up, you may perceive tighter bass with a silver cable because of its overall affect on the full sound spectrum.
I hope this doesn't confuse you, heheh.