Sounds like a decent chip. You should definitely not be unhappy with 5 ghz on AIR. It wasn't that long ago that people needed sub zero to prime at 5 ghz, and here we are running 4.5 ghz on auto voltages.

Is that BIOS voltage setting or load setting in cpu-z?

Unless you're trying to use sub-zero, I wouldn't risk getting another chip only to find out it is worse than before, unless it's pretested somehow.