Well, I just added a liq cooling system yesterday and over clocked my computer so far. So the goal you probably already know that the speed just depends on the FSB and the multiplier !!! The Main important goal is to get your FSB as high as possible and use prime95 and speedfan (to regulate the temp of your cpu) to make sure it is stable.
I manage to get mine to 3.45 Gig. So my FSB was 265 and multiplier set to 13x -- [Motherboard and etc hardware will vary]
You can self manage this yourself --> When you see window trying to boot but fails, try increasing your voltage " A LITTLE" ; can't stress that enough. If you manage to boot up windows and try openeing speedfan and prime95 with no freezing or unstable events happening, that over clock is stable so far. I would run prime95 for 10+ hours and if your cpu can run for that long of a stress, then you are fine. If not it will freeze on you and corrupt your speedfan file (maybe, hopefully not, but you can fix by reinstalling).
So now you are thinking what shoukld i do now? Well Depending on your motherboard --> you should probably increase your Motherboard Voltage (Northbridge Voltage) just a little, by .1 V and your HTT Voltage by .1 [Or you don't need to Increase your HTT voltage that much, up to your system]. And perhaps you should set your HTT link speed a little higher, For me it was 800 Mhz.
Now see if you can boot windows [for sure], and it should be able to run speedfan and prime95 correctly. So if you manage to do that, Run prime95 for 10+ hours to check if your settings is stable - then if nothing happens, you are Good---- GOOD LUCK!!!!
BTW if you are goign to OC this Cpu --> I RECOMMEND LIQUID COOLING --> IT GETS HOT
My Temperature from min load is 32 C to 49 C max load --> pretty good
I'm not sure I can go higher, didn't try yet since I'm still stress testing it
My Rig:
Motherboard: MSI K9a Platnum
RAM: 4X2 (8 gigs) OCZ SLi Ready [just a gimmick] 5-4-4-15 PC2-8000
CPU: AMD X2 6000+ 3.45 gigs atm
Cooling System: Swiftech Aquarium Kit Ultima ...something like that