I have a Asrock 990FX Extreme 4 and have had my FX-6300 at those speeds for the last 18 months now without any glitch's.
I have read of others having issues getting this kind of performance with other supposedly high performance motherboards!!
Typically I have mine set at 4.8Ghz ever since I got running.
I have had it to 5.0 and 5.1 (boot only) but you need a really good cooler to maintain those speeds.
I use using very cold air in the winter at the time.
I would suggest nothing less a H100 or better.
I also have a FX-6100 that can run 4.95Ghz on a H100 all day and night long Prime stable, but I did down clock that one to 4.75Ghz becuase it is my moms machine and she doesn't need the extra little edge.
That one is using a Gigabyte 990F UD3 motherboard with a XFX 6870 video card.
I had that at 5.0Ghz to but it really kicks up the heat at those speeds.
Meanwhile my CPU run's quite nicely at 4.6Ghz to 4.8Ghz on a Cooler Master 212 with two fans.
That range seems to be the sweet spot for those CPU's.
I am also using some very good G-Skill Ripjaws X at 2133Mhz without issues as well.
Don't waste your time on the older Athlon stuff if your budget allows.
I had a spare case and supply with an old GS7300 video card so I don't do any gaming with it.
For everything else it is a great machine and only cost me $400 from Newegg at the time (Xmas 2012) for the Heatsink, CPU, 8GB RAM, 1TB hard drive and Motherboard!!
I am using just a 350 or 400watt supply so it does hold me back a bit when I do Extreme overclocking above 4.8Ghz as does my cooler, But it worked and I did get it there.
I do have it registered on on CPUZ but I don't have those links handy at this time, sorry.
FWIW
jer