I have a S371, which is a custom modded S366 that is pretty similar to their new S372sxe, but without the fancy exhaust side turbine. I routinely blow the bearings out of it when turned up over 700HP, so I limit it to 660HP and it survives.
With their improvements to the exhaust side thrust handling and the new turbine, it can probably handle a bit more, so I am with Josh154: 750-800 HP will be the max if you want it to survive.
I am interested how the new exhaust side will spool. My S371 isn't too laggy, but if they can make this spool a bit better, that would be sweet. Really, though, I need to move to a compound setup, I can't get the power and drivability I want with a single.
The real question I have is would this hold up as the high pressure charger in a compound setup, or is it still wise to go to a S472 instead?