Sleetz :
Could you explain madmatt?
the 990 board is good but obviously not matx
the other two
the little asus will run a 8320 if you add a decent cooler that cools the vrm's ( I own the board myself) - however its an old 760g chipset & not ideally suited to 8 cores - its also only sata 2 which will limite data transfer especially on ssd drives.
the asrock - just pish poor quality mate & really old specced.
there is a massive lack of am3+ matx boards,the only modernish chipset one is that 970 series asrock I posted - Im not a fan of asrock but for matx its the best if not the only choice
Personally with an 8 core fx I would honestly advise against going with an matx setup.