Ground lift question

Hey all,

I have a ground loop in my system and I'm looking for the most cost-effective way to get rid of it (without cheating). I'm running a rack-style active crossover (ART CX310) into an old school 4-channel amp (Carver AV-64), and using them to bi-amp a pair of passive subs with a pair of Aperion towers. I'm pretty sure the problem is that the crossover is grounded (3 pins on the AC, TRS outs) and the amp is not (2 pins on the AC and RCA inputs). I'm using TS-to-RCA interconnects, and it says in the crossover manual that this should automatically switch the crossover to 'unbalanced' output mode... but it doesn't lift the ground.

Ideas? I'm thinking direct box, except that those all seem to be unbalanced in -> balanced out, and my problem is I've got balanced in -> unbalanced out. Can I wire it up backwards or is something gonna get fried? Does anyone sell a 'backwards' DI?