[BScout]

What Luke said (though loop sync is pretty pointless with the MTRX -- I run a total of 5 MTRX now on 3 systems with the Sync HD on each of them and there's no need for loop sync -- just WC out of MTRX to SyncHD WC in and WC out of the main MTRX to all other MTRX WC in; WC distributors are in use)

But, Artis, bigger question, how many HDX cards do you have? To get the full channel count out of a MTRX plus the HD i/O you need 2 HDX cards. Both ports for the HDX1 card go to the two ports of the MTRX (set pri/pri) and then your HD i/o is connected to HDX2 card on port 1. You then get 64+16 (80 total) channels in Pro Tools to access.