Yep; unless you need SAS support I would recommend onboard SATA first.
OP, I have the same HBA card as you, it gets toasty even just idling, and even hotter once you throw a load onto it. I measured ~10W power use just idling (no drives attached to HBA). I almost guarantee using onboard SATA will be more power efficient.
Even better, is if you can physically remove the HBA card until you need it.
Topton N5105
Yep, this board looks perfect for your stated use case! You give up a bit for the form factor, but just put those sweet sweet power savings towards your next upgrade.
One last thought - I've watched a few reviews of the Jonsbo N1 and I think there were 2 flaws with it: loudish stock fan, and if you are using all HDD slots drives can overheat due to bad airflow (front panel is solid - not vented - for some reason!)
Sorry, I was strictly speaking newer Intel SFF mobos vs the Haswell one I quoted. I get 15-18W idle with SATA SSD, 1Gbe, no PCI card/no HBA, and an ATX Gold PSU. Two different (i3/i5) Haswell era SFF PCs I tested are both in this range. Once CPU is used at all, they both jump up to the 25-28W range.
No specific recommendations for off-the-shelf offerings, but I see you're in Europe and concerned with power consumption? You may want to look at Wolfang's Channel on youtube - he has a few NAS builds that are extremely low power, and I've found his videos informative. Specifically, you will want to look at his "Building a Power Efficient Home Server" video.
Of course, the above is not useful if you're looking for prebuilt units.
About 275 Canadian Pesos for those keeping track. Wish we had the prices you guys south of the border seem to get!
In the past I've given up buying locally and instead bulk ordered drives in the US and shipping to a US address, then package-forwarding them over the border. Saved quite a lot, duties on HDDs aren't that high!