Cable for subwoofers

Just how important is it to use high-end costly interconnects for connecting your AVR or Amp to your powered subwoofers? I have two B&W subs connected to my Rotel AVR which has two sub outputs. I'm using a standard Monster THX subwoofer cable to the ASW600 (which has an analog internal amplifier) and an Audioquest HDA-6 COAX video cable to the newer ASW610 (which has a newer internal digital amplifier). The Rotel/B&W hi-fi dealer sold me the Audioquest cable when I purchased the ASW610 and advised that since the 610 sub uses B&W's new digital internal amps, a video coax cable is fine. Both cables are about 25' in length. What are your thoughts on this? Both subs sound fine with the exception of the ASW610 which seems to rattle at times when it's cranking. Do you think the rattle is due to the COAX interconnect cable I'm using? Should I match that with the other one (Monster THX)? Thanks.
No,the rattle may be caused by the sub being played louder than capable,or the voice-coil in the woofer may have broken loose.It could have been defective from the factory also.You could swap cables to verify just in case,but the cable theory doesn't make sense.Ask the dealer if the new one is supposed to play as loud as the old one.If yes,let them fix it under warranty.It may be something else loose inside the sub too.Hopefully all is covered by the warranty.I've had two defective subs rattle at low volumes when they were new.I never had a chance to drive them to hard.♫
You may want to give a quick check on the "tightness" of the screws securing the subwoofer's driver to the cabinet. They can work themselves loose and that *might* be your problem...

Thanks for the excellent replies gents. I'll try the cable swap. Unlike the ASW600 (which I did have to tighten the allen screws around the driver when I first bought that sub because it rattled also), the ASW610 has no mounting screws for the driver. I removed the back plate and looked inside. After peaking around the insulation, I saw what looked like permanent rivets with no way to adjust or tighten them. Perhaps by removing the back cover which attaches to the electronics/amp and then remounting it, it will not rattle with those screws now being tighter. We'll see. I am probably going to order an upgrade on the cable. If it still rattles, then yes I'll take it back under warranty for repair. I believe there is a 3 year warranty on the unit. Thanks again.