I think you'd better check nshos.com direct. Somebody there owns an X66. We sure dont. From the pictures, it appears there are at least 2 vibrato scanners in your organ, so mixing the wrong channels together might be rather strange. Alternatively, run each input to a mixer and slide pots to suit. You can pick which input goes to left and which goes to the right on the fly as the concert goes on. You might eventually want to mike those ToneCabinets in stereo. Churches usually put reverb to a tone cabinet in the back of the room, for a classical setup.
I picked up my 12 input Peavey mixer for about $100, sometimes you can get 8 input or 4 input units for less. Probably will have bad spots in the pots, of course, unless you buy a whole band system coming off the road as I did. Mines got both phantom power input for condenser mikes, and gain for dynamic mikes. Also has both XLR and 1/4 phone (low gain) inputs.