The computer will not put out sound, it will put out sounddata over Ethernet, the soundsource of the keyboard will produce audio from this sound data.

So there is only 1 audio source... This is the keyboard. The computer should start as they call it totally scripted, and you would not even neet a screen on stage, just switch it on and controll it from your keyboard...

At home you use a computer screen to setup and edit your sounds on the computer. You should be able to controll the sound parameter during a performance on stage directly from the keyboard, i.e. use a knob on your keyboard to changen for example a filter setting real time.

It can also be done by putting extra computer power inside the keyboard like mediastation and Wersi do, but for those players that dont want, need VSt's it would be a huge throw away of resources and money.

This way you get the best of both worlds.