True, locked Bartons have 1,65 Cvoltage for default. I also agree on the max.
Vcore thing - there's around 1.95 V running through my locked 2500+, making him produce nice (but by no means adequate ]
2350 Mhz @ speed of 212 FSB. Keep in mind though, that I took good care of cooling it before I did that. And thats pretty much it :P, dont wanna go further...
Regards!