AC captive cords???

just for kicks and giggles, you might try an "after" line cord. get an adapter and connect another line cord to the captive line cord. assume you have a spare line cord, the cost of the adapter should be about $25.00 .

Eldee: Applying money directly to the system, I love it! Cuts out so many tedious intermediate steps. Makes liquidity of the other kind easy too, but if it got out of hand it could put Audiogon out of business. Obviously higher denominations will sound best as you say, the ultra-high-end of course being OOP, NOS notes. Silver and gold certificates beat regular currency, with the $100,000 gold certificate the king of the hill...

Although it was for a captive power cord on a Cary SLA-70Sig tube amp driving a full range speaker with transmission line bass down to upper 20's (perhaps, not as deep as a true sub-woofer), the plugging of the captive power cord into the very highest version of the Mapleshade Records power strip (conditions without the appearance of being a conditioner) allowed the deep bass to become more defined, pitch accurate, and even deeper, by judgement of three pairs of ears (not confined to one head, by the way :>)
Not sure if this is an item with a return option, if you are not similarly rewarded by low bass satisfaction.
I would hesitate to clip short a captive power cord in order to attach the Mapleshade Records Pig Tail power cord option, although it is supposed to work, according to the website. It just seems so irreversible if you don't hear an improvement. By contrast, the power strip helps the sound of all component power cords that I have inserted, without any surgery.

Um, just to be clear, I was just having some fun with what Eldartford said. Sometimes we need a laugh in this 'serious' hobby. I'm a firm believer in power cables. For a serious answer to the original question, I had a similar issue with the captive power cords on the Marantz MA700 mono amps I use to drive the subs in my HT rig. I replaced them with cryo'd CDA 101 copper wire of 13 gauge net, and I did notice a small improvement in lower-bass punch. Of course the original factory captive cord was only 16 awg, so that probably explains most of the difference.