the fx 8120 is a great overclocker, had 1, so with a good mobo, and a good cooler, it isent worth the money if you look at gaming performance.
My motherboard is a GA-990FX and I have a standard Water cooling system
And what is a standard water cooling?
but then clock it, normally it will go higher then 3.8ghz.
I could run my fx 8120 at 4.2 on air, any higher the package temp was to high.
And on wc (H80i) it would go to 4.5ghz
Unless you can get a pretty good sale I'd stick it under the 'noticeable-but-not-really-worth-the-cost' category, although the Vishera has a bit more headroom up around 4.8-5.0
Could you take a picture of said WC unit, out of curiosity?
Also, once you start bumping voltage these suckers get pretty hot. My H100 has a hard time keeping the OC in range.
Bump it up to 4.0 and see the temp under load.when I had it at 3.8ghz it was 43c under heavy load