Seems like I should wait till next quarter and see what that z390 is like, in the meantime, what's the best way for me to raise my cpu from stock, using the bios or gigabyte mobo app? Nothing mental, I could go for 4ghz o'clock, I have the corsair aio at full pelt all the time anyway so not fussed about the fan noise, could be a good starting point to dip my toe into the dark act of OCing.
There are guides for those chipset boards to follow.
I remember using this one - http://www.overclock.net/t/1401976/the-gigabyte-z87-haswell-overclocking-oc-guide - and getting strong results.
I went near 5Ghz with this guide so 4Ghz should be simple, maybe even just a case of setting all the multipliers to 40X and seeing what happens.