Interesting signal path! I also have three H9s and have two different set-ups. My mono rig has all three in the FX loop of my Tweaker 40. My stereo rig uses my Mesa Boogie Mark V 25 with my dry tone out a 1×12 and my wet sound derives from the CAB CLONE SEND into my Onyx 1220i with two H9s each using separate mono AUX SENDS with stereo returns to my PA. This gives me a wet-dry-wet sound image which is killer, at least in my home studio, which is where I play most of the time.
i also love a compressor and use the carl martin in front of both amps.