6027TR-HTRF+(X9DRT-HF+) does not support standard PCI-E x8 or riser card for adding AOC. There is no space on X9DRT-HF+ motherboard with extra PCI-E cards. But you can have SMCI Micro LP card for AOC support. If you still consider using standard PCI-E cards, please use 6027TR-HTRF (X9DRT-HF) system. But X9DRTH-HF has fewer memory slots to support than X9DRT-HF+.