Are upgraded power cables for subwoofers worth it?

@sns Thanks for clarifying your setup. Since you have dedicated lines for 10AWG wiring, including lines dedicated to subs, I can see why a 10awg PC could help you obviate any possible current limitation, especially if the PC's that came with your sub came with were restricting their current requirements. (When I talked with REL, they explained that their PC's were sufficient for their subs.)

But I have to admit, your description helps me, as I've wired a new room with those kinds of outlets (and a dedicated breaker box), but I have not moved in there yet. When I do, I will reconsider my conclusions about PC's and subs.  In my current room, with a 20 amp circuit, no dedicated outlets, and wall wire that is 12AWG, I could not hear a difference with PC's, BUT that's likely because my setup, unlike yours, prevents me from hearing the benefits that you can hear. My claims about not hearing a difference were probably falsely attributed to the PC.

I suppose others reading this advice might take away the reasonable conclusion that if they have a setup like mine, they may also not be able to hear a difference from a PC (due not to the PC but to the wider system).

My guess is that most people will have 12ga with a 20a circuit. So, for most, a 10ga cord probably won't matter unless they have a high-power sub and an 18ga cord.  But if they have a setup like yours, the PC might matter. 

I appreciate this exchange. I'm learning from it. Advice is always relative to someone's setup, and you've made me understand the difference between your (amazing) setup and my ordinary one.

!0AWG is difficult to work with, generally the largest gauge that will fit most breakers and AC outlets, and for longer runs they certainly help with supplying needed current for those transients. For me, the easy part of PC for subs is determining gauge, 12AWG in wall, at least 12AWG PC, and so on. As I previously mentioned I've long heard differences in bass delivery to audio equipment, in other words resonant vs more damped down/tightened bass. First time I really noticed this was with an extremely expensive Elrod PC on some Cary monoblocks I was running at the time, I was amazed by how both the quantity and quality of bass was so different from the other cables I had tried up to that point. Ever since then I've been extremely sensitive to how bass quality is affected by PC's. I absolutely require a deep hard hitting bass devoid of even a wiff of the dreaded one note bass, bass should be tuneful and articulate in my book.

Now I will concede that in my system and some others the main speakers may be delivering vast majority of bass frequencies. With my Klipschorns, including modified crossovers and all drivers, careful placement in corners, modified top plates for max seal I get in room frequency response down to aprox. 32hz at my listening position, REL's crossed over at this freq, and this with only one of the hot wires connected to my monoblock amps, volume knob only two or three notches from minimum. So, essentially the REL's are supplying very little bass in my setup, vast majority of benefit I get is with sound staging, In any case, I simply want the sub to be an extension of the main speakers, coherence is paramount, and this important even with the little bass REL's adding to my system. So for max coherence I posit PC's  on subs should replicate those used on amps, and even preamps, gauges may vary, topology and metallurgy should match. On the other hand, I can envision a situation in which this may not be optimal, perhaps some systems may require a different recipe for amp/pre vs sub.

Used to be the power cables don't do much camp, then I tried a few power cables. 

On my HT setup, I noticed that after installing PC's to my SUB's and amp, that the power draw on my power conditioner went up, quite a bit. At idle everything is drawing more power. When things start to hit, my current draw jumps up way faster and higher.  Sound wise, it's cleaner, but didn't really notice much more, maybe better dynamics.

The sub on my 2ch, took measurements before and after. Test tone, measure, change cable measure again. Got almost 2db higher on the test tone after a cable swap. Bass felt deeper, fuller. After a couple days, I turned down the gain on the sub.

My 2ch sub is a Martin Logan sub array, it had a ok 14g cord. Swapped it with a 10g. 

Weirdly, when I swapped PC's with my streamer, didn't really notice anything. Same for changing power supplies on my TT, no real difference. 

Yes.

It's been argued that there are better "bang for the buck" power cables than Audioquest, but can't think of a single occassion where their $100(+/-) cables have not provided a sound quality inprovement to anything I've connected them to.

Regarding wire gauge, the current limitations to your gear are:

• Breaker size at the panel (usually 15-20 amps)
• Wire size in the wall (should be right-sized for the breaker, so usually 14-12 awg)
• Power cord gauge to the equipment (no need to be bigger than what's in the wall)
• Fuse size in the equipment

Your equipment should not see more current/amperage than the limiting factor of the above conduits.  Considering even larger amps rarely input over 10 amps of current, a case could be made that a 14awg power cord is plenty big for even large power amplifiers.  Not trying to change anyone's mind, but that is what the science says.