Thanks to creepas for sharing the BIOS, it works. Also thanks to all who posted confirming kaby lake CPUs work. Was worried my cheapo i3 (a mistake I know) would blackscreen on it, like it did on the older BIOS mobo came with.

I got up to running 6 cards (waiting for parts), 1x480 MSI Armor 8GB, 5x580 MSI Armor 8GB. Issues I ran into and had to fix:
- 1 long beep 2 short beeps, black screen after flashing - flashed at least the main video card back to original bios so it could get to windows.
- wouldn't get to windows after 5th card - had to enable Gen 1 in BIOS to proceed
- flickering back to blackscreen while on windows - forgot to flash one of the cards back to original
- 1 long beep 2 short beeps when booting with 6 cards, running headless rig without a screen - not solved this yet. it boots and mines, but the dual claymore miner loses temperature control. annoying.
- heat. haven't done much about it yet. this coupled with loss of temperature control means 5 original vbios cards run about the same as 4 flashed/customized with temp control.
- PSU cables are way too short for this. Got enermax 1700W platinum on the side of mobo - the 8pin cables can only reach 4 closest risers so needed to find and order 3 extension cables off aliexpress.

Hope this helps someone.

Few questions as well:
-is "fake screen" hdmi cable a must for headless rigs? dual miner worked ok with 4 cards and no screen, but past that it can't see temps and control mining intensity unless there's a screen attached.
-fans? I got a precut frame with slots for about 9 default PC sized fans, 5 top GPU row 4 bottom. Should I fit those or get a huge floor fan behind the rig and be done with it? I've been reading some but so far all I took away was that ball bearing fans should last longer than sleeve/lubricated ones. Any suggestions would be welcome.

edit: can run custom VBIOS after all, got too scared of the beeps initially. had to redo the driver signing with atikmdag-patcher-bios.exe

Could someone confirm they made 6+ GPU work with a Kaby Lake CPU? I'll have the time to try myself in a week or two, would be nice to see more information on this. Hope I don't have to downgrade the CPU... splurged on it.

Edit: v1.6+ BIOS supports Kaby Lake, is the custom BIOS based on that?

Any reason -ttli doesn't work for cards past GPU0? using "-ttli 62,62,62,62 -tt 60,60,60,60" for example.
Mining on Win10, miner version 9.3, got a mix of rx480 and 580 going. Tried -ttli, -ttdcri, -tstop, but all seem to work on #0 only. Would appreciate any pointers.

Edit:
I was connecting with Remote Desktop Connection and that creates a dummy GPU that really screws up the GPU indexing. Tried Teamviewer but it doesn't work without a screen/HDMI dummy attached. Using Splashtop to launch miners for now, can do the rest on RDC.