I have a Biostar TB85 and it's a good motherboard. Easy to setup and it's been problem free with up to 6 cards.The ASRock H81 BTC Pro also has a M.2 slot and overall probably has somewhat better build quality. What I don't like about ASRock boards is they require you to use the 4-pin molex PCI-E supplemtal power, even though it's not needed when using powered risers.
I ordered two mobos as i was getting a deal on them, i am planning to sell one, should i just use the tb85 for myself? i agree about the 4 pin molex, that seems useless, what cards are you running on the tb85, i am planning to run 6x1060, should be fine right? not much of a driver issue?
Right now on the TB85 I have 4 RX 570 and a GTX 1080. No problems mixing both drivers on Windows 10, though I found the Nvidia card works better if if it's in the PCI-E x 16 slot.
Either one would work fine for six cards. Personally I would keep the TB85. If you want to use a more power efficient newer processor, you could also try the Biostar TB250 LGA 1151 motherboard. Windows no longer supports security updates for anything newer than Skylake CPU's on Windows 7, so if you want to use Windows 7, the TB85 or H81 BTC Pro is a better option.