The FX processors aren't that great and they have a lot of compatibility problems that no other processor type has.
It is an FX slot and you would think that if you just bought a motherboard that says FX on it that it would work, but unlike every other processor it isn't that simple with FX.
Its quite often that a FX board doesn't even recognize a FX processor.
I usually just suggest to stay away from FX because of all the problems with them. They flopped in the marketplace for a few reasons, most of which were good ones.
For processor + motherboard I would suggest you get an i5-2400 and a Gigabyte 1155 motherboard in the $90 - $125 range.
- Edit - Those two things I said should come to about the same $270.
That would be a whole lot more powerful, it would make less heat, use less power, and the motherboard is guaranteed to recognize the processor from the moment you plug it in.