The fusion 205 "zone" control is nothing more than fade with only a single pair of RCA cable outs. So you first have to have all the speakers on external amps. Other wise, zone control like tower volume, will also control the front, or bow speakers if still on the head unit.

Im not opposed to a hi to low converter, providing the amp thats getting those RCA's, can compensate for that signal. Most Kicker amp, which still come OEM in the Moomba in 2016, will. However, the converter itself can also be a source of unwanted noise, as is anything we put in the signal patch. I have not used the fusion converter, so no experience with it.

This is where i like a dual zone control like the Kicker ZXM-RLC. It only needs that single stereo RCA output to give you dual zone. Rather than divide the voltage, it is a 9V per chnl line level driver. Requires short RCA cables as the brain gets mounted by amps and knobs connect via data cables.

Knobs can be surface or panel mounted.

Easy to pair the woofer with either zone, your preference, or if the woofer amp accommodates a sub level control, you now have 3 zones.