The problem with FX8 is that certain air coolers don't play well with it due to the core structure/layout/size of the die.
That's why I would usually recommend an AIO because that way the block pump part is huge and covers the CPU well.
I also would urge caution and say don't go over 1.5v. The thing is you won't even be able to get near that voltage unless you have grade A cooling. And you will be fighting lock up temps all the way at those voltages.
I found that I could actually clock my 8320 higher on 1.47v than I could on 1.5. It just froze all the time on 1.5. Sometimes you can be too heavy with the volts and it degrades performance.
Looking at your overclock you seem to have done it on multiplier alone. This is never a good idea as more multi means more volts usually on FX 8. I suggest turning your multi down as low as you can then working on the FSB then add multi/change memory divider as you go. I found I could clock way, way higher using FSB over multi.
http://forum.overclock3d.net/showthread.php?t=70108
Take a look there but you will see that I got almost 5.1ghz using 1.47 V with LLC on extreme (hence the 1.488v reading) with a FSB of 230 and the multi on 22.
I had a very, very good chip. I could boot into Windows on a H100 @ 5.35ghz but as soon as I moved the mouse it would bomb.