check coretemp, that should tell you the exact vid (stock voltage) for your chip
Core Vid, next to Technology.
All on the first tab.
CPU-Z reads the voltage wrong a lot of the time, I wouldn't trust it.
If an E6400 runs at 1.325v stock then there's no way an E6600 runs at 1.4v?

1.325v - 1.35v is stock.
Totally depends on how good your cooling is how much you can take it to. I've gone upto 1.4v with my E6400 and it's rock solid at 3.3ghz and runs cool. You can go upto about 1.5v I think with very good air cooling but no more...

well your RAM is rated for 800Mhz so should be fine to run at just that, leave the timings on auto - or if you are having issues you could slacken them off a bit, and set your DIMM/RAM voltage manually to the vendors recomended. You should be fine then