I'm using Eist for Vcore and multi change with overclocking and it's working fine as long as you don't want to go higher than stock volts. You would have to use RM or Crystal for that.
To my knowledge C1E is disabled in bios. Well I can't be bothered to do a maintainance boot right now...
Idle: 2Ghz @ 1,1V
http://img140.imageshack.us/img140/9697/idleui2.th.jpg
Load: 3Ghz @ 1,325V
http://img140.imageshack.us/img140/1171/loadsk9.th.jpg