Should I get the Extreme3 R2.0 or the Extreme4
At first I wanted to get the R2.0 but then I googled a comparation search and found out that the Extreme4 has extra 8 core support, don't know if the R2.0 has extra support for an 8 core since it wasn't notified.
It is supposed to be a temporare motherboard for my FX-8120 no SLI
have you checked this comparison?
Also check this article: http://www.tomshardware.co.uk/answers/id-1891470/asrock-970-extreme3-motherboard-good-motherboard.html
It's pretty much what you've asked
The spec for both are here: http://www.asrock.com/mb/amd/970%20extreme3%20r2.0/http://www.asrock.com/mb/amd/970%20extreme4/
Only difference I can see is that extra pci-e x16 slot meaning sli capable (good if you ever want to upgrade)
In short: if you aren't overclocking too much both mobos will be fine. They both support 8 core the same but i'd go for extreme 4 for extra pci-e x16 slot. Also they look like better heatsinks (although with no oc it hardly matters). You just have to get over that blue/white colour scheme