Problems with Revel B15 Sub

I am running balanced XLRs from my Bel Canto PRe3 to their REF1000 monoblocks. Problem is, when I then run them to my Revel Sub then back to my power amps the sound becomes slightly grainy and there is audible distortion on specific frequencies of women's voices. This does NOT happen if I run the XLR's straight from my Bel Canto PRe3 into the REF1000 monoblocks.

So I borrowed another Revel B15 sub--and exactly the same thing happened! I've very carefully checked all settings on the EQ of the B15 and the drivers of my speakers--they are not blown.
The only things I could think of are:
1) The Revel is running into a different wall plug without conditioning and a cheapie AC cord for now (all other components are run through a Balanced Power Technology CPC). BAD POWER??
2) The XLR's run right behind and below a large Sony CRT TV, over the cable wire and the main plug for the BPT CPC--INTERFERENCE??
You are running the signal through additional cables, connections, and, I suspect, a crossover in the Revel sub. A recipe for degradation of the sound. Does the Revel sub accept high level signal straight out of the monoblocks? If so, that would definitively (aka REL philosophy) be the way to go. If not, does the Bel Canto Pre have a second set of outputs to drive the sub? That way you are not messing with the signal that feeds the monoblocks.
Good Luck,
I agree with Arni.
I tried a similiar approach as you just did. I put the Revel crossover between my Ayre preamp and Ayre amplifier. I found that I lost a significant amount of detail and dynamics. I would have thought that I would have lost some detail and gained dynamics.
Well, we discovered what it was--the REF1000s monoblocks each have a switch to choose between RCA and XLR input--and they were set on RCA while using XLRs. Duh. Now the sound is much better.
My Sonus Faber Guarneri arrived today and we'll see what the introduction of a sub does there--I do not want to degrade their beautiful sound. Thanks for the responses!