USB virus - Room for everything?

[durrdurrdurr]

Hi again

So im wondering about using multiple virus "synths" (in lack of a better word) simultaneously with usb as the only way of getting the sound into my DAW.

On a recent project i have 6 different synths loaded up and playing. What im experiencing though is that some of them have a tendency to disappear when all of them are playing. Its like its not enough room for so many synths, and hence the virus is squeezing some out. Does the USB mode have limits to what it can do? I mean, the VST thing has 16 different "synth channels"... eq´ed correctly can it run that many sounds through the usb at the same time? And if so, is there any settings to control this?