grab a good barton 2500+ and you'll be able to get to 2.2ghz at stock vcore, 2.3-2.5 is what i would expect a barton i plan to buy to do at less than 1.8V
1 person i know got his to 2.5ghz at default voltage, this is his stepping AXDA2500DKV4D AQXDA0315TPAW. He was using an a7n8x(rev 2.0 i think but not sure)
AQXCA is the stepping for 3200+ but barton 2500+ have it now aswell, that's the one to look for i'd say