Thanks for the response. My AVR has two subwoofer outputs, but I’ll have to check the settings to determine if it manages them together or separately. My main concern (which was brought to my attention by a local shop owner) is that I “definitely should be using identical cables” for both subs for optimal performance. I’m guessing he was probably just trying to sell me another cable.
Ya... not a thing. Don't get me wrong, if it were me I'd try to match up as much as possible... but no harm will come of it. Length of cable doesn't matter, really, even if 6' and 25'. Truth be told, its just nicer to not have coils of cable wound up and tucked away. Get the right cable for the run plus a few feet for slack: that's it.
If you really want to get crazy, get a pure copper conductor as opposed to CCA (Copper Clad Aluminum) or CCS (Copper Clad Steel). They should all be very affordable. If you have to run parallel to any power cords or power strips or bunches of other cables, perhaps something shielded.
Still shouldn't cost anything more than these:
This Digital Coax Cable is made from premium quality RG-6/U with double copper braid shielding to prevent signal degradation caused by EMI and RFI interference. This cable is ideal for conducting S/PD
www.monoprice.com
(What I use. Good cables, affordable and they work.)