I use 2 ADA8200's with my Quantum and all works fine. You have to make sure that the Quantum is the 'Master' by ensuring in UC that the clock is set to "Internal". On the back of the ADA8200 you need to set it to Slave ADAT. You will need 2 ADAT Cables for both IN and Out. Also, the ADA8200 only work with 44.1 or 48khz, so if your Quantum is set to 96khz then it isn't going to sync.
I have mine set at 48khz and both of mt ADA8200's at 48khz also.