Just wanted to post a little bit of my own experiences with my 790X UD4P in case it might help someone.

I was overclocking my unlocked 550BE by just bumping up the multiplier by .5

Once I got to 3400mhz, I got prime95 errors after 7.5 hours (I ran prime95 multiple times, and the error consistently showed up after 7.5 hours).

Everything in BIOS was at stock except for the CPU multiplier. Before bumping up the CPU voltage, I wanted to try something else.

I increased CPU NB VID from 1.1v to 1.2v (based on the advice in this thread ) and I increased the CPU NB frequency from 2000mhz to 2200mhz.

It seems that my system is rock solid stable at 3.4ghz now(passed 10 hour prime run).

Hope this helps!