If you've got an aftermarket cooler, the new AMD chips should be good up to about 1.45v or even higher. I wouldn't go any higher than that personally... my chip hits 50°C at the moment if i try and run it at any higher than 1.4v...
The 955 should be able to get 3.8 or even 4, since its stock clock is higher. Try a Prime95 test to see what temp it gets to after about an hour... The Heat boundary for current AMD chips is anywhere between 40 and 55°C.
Basically, anywhere that says "your voltage should be on..." is just a guideline. If yours is stable at that, then cool. If not, you've probably got a bit of space to boost it. Just keep an eye on your temps. If they hit 55 within a few minutes, then you need to stop and lower the voltage.