I hear more of a differance than a percieved reduction of noise and gain differential on the XLR outs. The music has a "fuller quality", like a better attack on the mid bass. This I noticed on the LR outs, don't know about the sub out, but suspect it's performance is better as well.
Why not just use the XLR to the behr, keeping it mono (which it at the rca anyway), use your XLR to rca adaptor out to a nice splitter like the outlaw one. If you keep your subs is opposite corners, I suspect the eq requirement won't be different for each. (you measure at the listening position anyway, yes?) Like this, you can use the remaining channel for the center perhaps...