Thanks, Linjo.
For the AMD part, I made it work by plugging a real monitor to the graphic card, then remotely control it using TeamViewer. By manually set the AMD graphic to Primary now I can run my workstation applications.
But the TeamViewer protocol (I don't know the name of it) really sucks. Besides there's no zero client using TeamViewer.
Also plugging four 24-inch monitors behind every server is not really feasible in the server room...
Microsoft RDP does not use real GPU either...
Really no way to use PCoIP now?
HP guys tried to sell the RGS solution but I've not test it yet.
Most my applications work great on AMD FirePro cards and not so well on NVIDIA Quadro cards. So I'd prefer to use AMD FirePro cards.