It's going to be tough (i.e., expensive) to beat the low end of the 255s, Joe. If the fact that they crap out at 4,000 rpm doesn't bother you, you might be better off leaving well enough alone. Better mileage might be had, but you can buy a lot of gas for what you might spend with a cam upgrade. Not sure the return will be there. Also, 110s run hot, no matter what, IMO. Don't think you will see any night and day difference in that from a cam swap.
All that being said, as has been pointed out, the ESP covers more than just the motor. So far, I've made the choice not to get one, but even if you did extensive motor mods like me, they couldn't deny a radio claim, for example. Though, the return might not be there on that investment, either.