Matt,
erm, I just plugged it all in and it worked.
Seriously, no signal booster used. I used the rear pre-outs from the headunit in conjunction with the ICT loom.
Red/White from the ICT connector to the RCA fronts (Headunit), Yellow/Black on the ICT connector to the Rear/Sub RCA (Headunit).
Made sure I turned off the internal amp in the headunit and told it to use the RCA outputs for rear speakers and not subwoofer.
The headunit is a DPX 503U for reference, so its nothing fancy really.