Well the motherboard doesn't ues a 990fx chipset but it should be just fine anyway. Since this CPU already has turbo to 4.1ghz you should be good to go. Start by disabling turbo core completely and increase the multiplier to 4ghz, check for stability and increase voltage if necessary.
In my opinion, an increase of 500mhz is worth it, just watch temperatures and dont go above 63c for to long as it could throttle itself and make your oc useless.
Just keep increasing the multiplier and fsb if you want too, all CPU's vary so there isn't really a "good overclock".