cbturf,
I appreciate your insight into the 2320 v. 2520 power differences. Unfortunately, the RPM differences are different at the rating point so we do not have a direct comparison. Since these engines typically make more peak torque at lower RPM I suspect if they both shared the same 2600-2650 RPM rating speed, the difference would be much closer. Thusly, if one could tune the 2520 to a 3000 RPM rating speed, I doubt it could make 50 lb. feet of torque. I would expect the 2320 to make around 45-46 lb/feet at the lower engine speed, making it a pretty negligible amount of difference. I was intrigued to find that the slightly more narrow tires of the 2320 seem to grip a little better in gravel or loose dirt than do the fat tires of the 2720 I tried. The 2720, which was ballasted, lost traction more easily up my drive pulling the same size box blade. I suspect to gain full advantage of that machine's power one would have to add substantially more weight. I can say also having tried a 2305 during my testing, the 2320 felt much more powerful and pulled the BB more easily, belying the fact it reportedly has the same engine and tuning (which I doubt--but cannot prove). I also subscribe to the more power club, but unfortunately it might not be as profound as it might seem, and two PTO HP difference for the price difference does not seem to be justified. I think JD has done a fine job of marketing in how they rate these machines--to make it seem as though there is more difference than actually is present. This comes from an owner of two 3720's, a 4520 and a 4310, the 4310 being the only one I felt slack on power. I really wanted to love the 2720, and I did like it, but there was no way I could justify the difference in price for what I saw as a very similar machine.
John M