Originally Posted by Baskt_Case
If its taking 1.42v to hit 3.6GHz, your probably about to hit the wall.
These chips get to a point where it takes huge voltage for minor gains.
I can do 3.6GHz @ 1.36v, and used to be able to hit 3.75GHz @ 1.46v with no possible increase after that. Tried all the way to 1.55v, at which point I could no longer run 3.75GHz, so watch how hard you push it.
I was running stable @ 3.75GHz on the stock cooler and never broke 48C core temp. So you might be pleasantly surprised how far you can go on the stock piece. As for recommendation, you'll need someone else to chime in.
This is the case with my X2 255 as well. Hits a wall right around 3.8ghz and 1.46vcore. These chips run super cool, which is why I think they use such a tiny HSF. No need for something bigger.
Keep an eye on core1/core2 temp. I think I read that you are good up to 70C, which means generally you will hit a voltage/clock rate max before you start adding significant enough amounts of heat to get the temp that high. For me, there was no difference in overclocking ability with either a reference BE cooler (has heatpipes and would manage mid 40's under full load) or a massive zalman CNPS10X (where it never broke above 41c at full load). It just could not take advantage of the additional cooling to get a bigger overclock. I have yet to try it with my water cooling rig, but it may be fruitless to even attempt it.
So the short story is that an excellent air cooler might get you a small gain over the stock unit, but unless you chill to sub-ambient temps that "wall" will still be there.