I recommend the 8370 (personally 8320) over any 9xxx unit.
You may wish to get a Xeon or i7 processor though, as you are upgrading your motherboard already.
A Xeon 1231v3 would be a cheap option to high multithreaded performance, the i7 6700k is a step up from the Xeon, but for that price you should look at a Haswell-E i7-5820k. Both of those i7s will offer phenomenal performance plus the use of DDR4 Ram.