Your system is certainly capable enough to get play many more voices. A few things you can try.
First, use only dry instruments. Make sure the auto-convert to 32 bit in the options page is not enabled. Raise the ASIO buffers on your sound card and disable DFD (you don't need it with all that RAM). See if that makes a world of difference.
If not, it may be driver related and we would be happy to call you and troubleshoot the problem.
i did change my soundcard to a delta 1010. i still have the same problem but more on the clips and crackles.
when i was using the aark 24, i also experience some sort of 'tripping' in sound. i thought it was in the sound card having problems so i changed it to a delta 1010. unfortunately, my problem didn't change. it couldn't be volrage power because i have been running the system on the same one for a long time now.
the cracks and clips, i've experienced before. so what i do is i shorten the length of the flute which is where it normally occurs. or any instrument for that matter. somehow, it gets fixed. but whenever i have the full orchestra going on, it never fails. the crackles. i just hear them.
the thing that's making it worse now, is the sort of 'tripping' sound. kinda like resetting the sound card and makes this LOUD pop. this is the first time it happened.
0 db in Kontakt equals about 80 in CC7. Obviously you don't want to go above 80 or you get clipping. I use 60 as a starting point because as you add instruments, the volume is additive. Each instrument added will increase the volume level. Fortissimo sections will usually hit just about 0 db on a full orchestra and sometimes even more.
Normally I don't use CC7 at all in GPO but use the volume settings programmed as they are pretty well balanced. I usually setup other libraries using CC7 such as SAM Solo Session Brass and QLSO at between 55-60 which is right in the ballpark with the GPO volume settings.