I do believe what you did are correct steps. However, I had one query on the below comment:
I have tried to VMDP the onboard VGA, but ESXi was hang half way after reboot.
If you are mentioning about VM-DirectPath, then if you have given that card as the passthrough device, the on board VGA card is now taken out of the kernel boundary, meaning that the display is not for kernel anymore.
The reason you are seeing a hang is "actually" not a hang, but the ESX is proceeding, only you are unable to see it in your display since it had been taken out of kernel boundary.
As Linjo pointed out in the posted community thread, you can use PCOIP to have multiple monitors for a VM and you can pass through you "ADD-on" graphic card to achieve this purpose.
Another easy method would be to access through VNC and use multiple monitors.