X58 is too old and is likely limited to 5-6 GPUs.
H97 should work though. Does it even boot with more than 6 GPUs? If it does, your OS is likely the issue.
You might be able to get 5-6 cards with the small boards, but YMMV. The chipset doesn't really matter I think, the multiplier combines the signal of all 4 cards into 1 lane.
Yea I figured it lately that x58 can only handle up to 4 GPUs.
I have a Gigabyte B85M-Gaming 3 motherboard, it works fine with 6 GPUs, but with 8 GPUs it just fails to even load into bios. That even with 4 GPUs plugged into PCIE1x slot via extender! so this means chipset is limiting its usage to 6 GPUs.