What kind of compatibility is required for PCIE 3.0?

None. PCIE 3.0 cards will work just fine on 2.0 motherboards. To get the PCIE 3.0 enhancements, the motherboard must support PCIE 3.0. You will not notice a difference with a 2.0 board v.s. 3.0 board in all likelihood if you are using this for an HTPC. I have this card currently on a PCIE 2.0 shuttle motherboard with no issues.