So I switched out and tried the analog cables and it still didn't work right off the bat. Had to check some more channels in audio pref to get all the sound that I wanted. (Sorry, should have mentioned I have Z-5450's 5.1) Everything seems to be working fine now though. So for a summary, I'm now running them on analog with all six speakers working just fine. Thanks for the help guys.
Main: i7 4790K - Z97 mATX - 16GiB DDR3 1866 - GTX 980 Ti - 256GB 850 PRO - 500GB 840 EVO - HGST 3TB - U2415 - Win10 Pro x64
Work/Play: 2015 13" rMBP