What is your temperature under load, i.e. Prime95 or similar loading. I have a barton at similar speed and Vcore and while my idle temps are in line with yours, I see high 40s under load.
You'll probably be OK increasing Vcore some more but keep an eye on your temps at load. Once it gets in the mid 50s, your starting to play with fire and the stability goes out the window (at least in my opinon). Once I get to 1.8 volts, I get a lot more heat and very little additional speed. On my CPU, its just not worth the extra heat over 1.775V.