Well, we didn't use an LOC in the final version.
When we tapped in after the DSP amp, in the initial install, we used Soundgate LOCHVAs (actually a Navone piece, now discontinued).
Sounded pretty good.
Then we took out the DSP amp and ran the audio out of the HU tuner module in the back straight into the aftermarket gear. We added rear outputs from the module to the aftermarket gear, since the tuner module has only L and R out in a DSP setup 9in the DSP setup the fader lives in the amp and is controlled by the HU through the databus).
We did use an IsoMax "gli" but at $200 for ground loop isolation it's hardly an LOC
