Hi, thanks for the quick responses!
DG, I know my sound card is not the best solution, it's what some would call a 'gamer soundcard'. I've had it for many years now, but I've never had problems before. I've been using Asio4All for 5-6 years now, before that some generic ones, and I must say Asio4All has always worked well in combination with my X-Fi. I have no idea where I can get another soundcard from, apart from buying a new one...
I moved to a slave+master solution only a few weeks ago, before that I was running Cubase 7 + VEP + MIR on one PC. I had quite a big template as well, +-8 PLAY instances, VI Pros, +-10 Kontakt instances with multi-timbrals fully loaded. Asio4All worked flawlessly with this solution (same soundcard). No matter what Plugins I used, how many inserts I had, my asio peaks and CPU usage were fine. My CPU was only peaking when I activated MIR, but that's to be expected :)
My audio plugin problems aren't as harsh as yours mohurwitzmusic. I can insert up to 40-50, and then the peaks are unbearable. But my CPU isn't affected AS badly, it's mainly the asio peaking. But it seems it's not just my X-Fi having that problem.
I jumped from Cubase 5 to Cubase 7 and I haven't really had any problems since. I find it is much more stable than before, and as I posted a bit above, I used Cubase 7 + VEP before using the audio plugins, with no problems whatsoever.
So it's either the audio plugin itself causing the problem, or my soundcard + asio4all + audio plugin as a bundle. My only current solution would be to evade audio input plugins and use MIR in Cubase, simply using the outputs of the different VEPs there. If I do find a different solution to this, I'll be sure to post; I don't fancy buying a new soundcard...
If others have a possible solution, it would be greatly appreciated :)
Cheers