I'm using 2 of these, for remote sub and treble control...
PC-> MAUDIO FW 410 -> JL CL-RLC -> SYMBILINK -> CH1/2 ZAPCO DC360.4 -> TWEETS
PC-> MAUDIO FW 410 -> -----------> SYMBILINK -> CH3/4 ZAPCO DC360.4 -> MIDS
PC-> MAUDIO FW 410 -> JL CL-RLC -> SYMBILINK -> CH1+2 ZAPCO DC500.1 -> WOOFER
I use windows mixer for main volume, not the best solution, but it does the job for now.
What you are planing to do should work fine, you also get the added benefit of the increased volt output (2X line driving) in your case, so you can run your amp gain low for less noise.