I also use a 192 I/O and a 96 I/O with my HD3 system. I reserve the 6 remaining outputs of the 192 for Hardware Returns and use the 96 outputs for 4 discrete headphone mixes. Works for me. I am sure there are other options. If I do not need Hardware Returns, the I use Outputs 3 thru 8 on the 192 for Mono "More-Me" sends for pesky vocalists and electric guitarists! Hope this helps... Cheers, Ron Fairchild
www.ronfairchild.com