why don't you install the better a/c cable and leave the ground wire unterminated. the ground loop is controlled through the rca and typically through the preamp to ground. i performed that upgrade to a pair of LO9-M's that i had. (you may want to consider changing the binding posts also while you're in there)
Kenwood/Trio L05-M grounding
I have a pair of Kenwood L05-M monoblocks & I'm considering replacing the 2-wire zip cord power cords with something a little bigger/better. The Kenwoods have an interesting feature, though: the power cable is ungrounded, but there are binding posts on each for a ground wire. The owner's manual say to connect a wire between these, but not to the wall. So the question is would it be evil to just ground them individually, using a 3 conductor power cord? I'm sure that there was a reason why the designers wanted to connect the ground plane of the two amps, but I have no idea what it might be & I don't know if defeating that would have some horrible consequences.