well 65 TDP is for the entire "desktop" part of the lineup. so you can assume that if the highest rated conroe is say 2.66ghz (and it could be higher) that that would do 65watts.
yonahs only run at 2.13 max, and those are under the 31watts or whatever. given the conroe can have 4mb of cache, and has more instructional units and higher speed (which is linear so at least 2.66/2.13 difference) and im sure a good bit of the extra TDP is there.
not to mention the yonahs are mobile chips and probably binned as such. they probably could make a 2.4 ghz yonah with say more voltage , but since voltage is squared in power use calculations it'd probably push it to say 45-50watts. i mean i have no doubt a conroe at say 2.0 ghz, with 2mb cache etc might use maybe only 40watts or less.