As this is a bronze rated PSU and not a modular one. I'll recommend not using any adapters to gain more connections for more GPUs. However, I'll recommend you to invest in a Gold rated PSU, Corsair RM850x is a personal favourite of mine. It can easily handle 8x GTX1060, and way durable to handle 24hr operation, so you won't regret investing in one.
I'll take a look into it. I wonder if this Bronze unit (
http://www.skytech.lt/m12ii750-evo-seasonic-m12ii750-evo-edition-750w-plus-bronze-retail-p-294241.html) is worth to get while saving 40EUR compared to Corsair? My wall draw will be max 550W.
Using SATA connectors for risers is a BAD IDEA, SATA connections are not rated for the 75 watts (nominal, sometimes HIGHER) that a common GPU pulls from the PCI-E bus.
Well I am running my GPU's not at full capacity, but downrated to get max MH per Wh of electricity and SATA wires are cold (with 3x GTX1060). On the other hand which connections are preferred to power risers?
PCI-E 6 pin to feed the riser is best.
Molex is tolerable, the connectors are at least rated to handle the 75 watt draw mining cards normally pull from the PCI-E bus (the connectors themselves are rated over 100 watts but the WIRING to them is usually not sized for that unless you limit to using one connector per chain).
SATA is bad, they are only rated 45 or so watts MAX, using them is a serious risk and has a significant probability of causing overheated connector and MELT/BURN issues over time.
There is NO way to "do it right" using SATA on risers, as there is no way to control how much power the GPU tries to pull out of the PCI-E BUS connector - dropping the TDP normally drops the draw out of the PCI-E BUS connector on the GPU, NOT the draw out of the PCI-E bus.
I use almost all Seasonic X-Series Gold power supplies in my rigs, but I have a few with G12 Gold series on smaller machines - they are good power supplies.
The M12 Bronze series should be comparable on reliablity (VERY good), at a small cost in efficiency.
I would be very cautious on Corsair - they have widely variable quality between their different lines depending on who makes each line (some are Seasonic or Super Flower made and very good, some are just junk).
I would avoid Coolermaster, can't remember ANY of their supplies being made by a GOOD manufacturer.