I was planning on trying this myself, just to see if my Wolfdale could do 9*400 without increasing voltage significantly. I figured in the long term (ie more than a few hours), it would be untenable owing to my stumpy cooler (the Xeon E3110's stock cooler seems inferior to even the Core 2 Duo E8400's). Of course, at that time I was still getting 15 C temperatures in my area, but I waited too long, and now it's June, and today the forecast is 27 C or the like (I don't have air conditioning in my flat). So I might not be doing it any time soon.
If you cpu is good, you'll probably get 3.6 GHz at very close to stock voltage. But I'd worry about how much heat the stock cooler can dissipate.
I'll be very curious to see your results. Most enthusiasts (understandably) run aftermarket cooling, so it's hard to get data on how far the Wolfdales will go with stock cooling. If you look at FrostyTech's comparison, you'll see that Intel's coolers are a good deal inferior to even the $15 aftermarket solutions.