Yes, this I know too.
Under XP you can install more soundcards BUT you can not use the all cards under ONE application.
I have here Cubase SX, Nuendo, Logic 5.5.. but when I start it I can choose only ONE soundcard of the two Delta 1010.
The mixing system will remain always under one soundcard.
With the same hardware but installed the Linux OS with this patch, we was able to see under Jack connection ket the all 20 Inputs and 20 outputs + the USB Audiophile M-Audio audio card.
All the music multiple application opened was able to share the all IN/OUT in the 3 audio cards togheter.

My question was aking you IF under XP give one virtual driver solution that will merge the all instelled audio cards for ONE application, like Cubase or Nuendo.
I wil try to fix this issue under wirnows OS too.