I don't have any personal experience with this, but I've read a number of reports of batches of the Won Titaniums actually corroding in saltwater.
I think for a while they were getting bad batches of titanium or lesser alloys.
Perhaps they've upped their quality control since then, but I wouldn't bet my tank on it.
Personally I'd stear clear of anything metal that will be submersed for long periods, with the exception of a titanium ground probe. Either Stealths or Theos would be my choice. I've read recent posts of bad quality control on the Stealths: with internal seals leaking, superheating the internal saltwater, and the steam eventually blowing the temp dials off and frying the tank. No personal experience with this problem... yet.
If it can happen- it's gonna happen to me.
A seperate temperature controller, single stage is fine, (unless you forsee adding a chiller in the near future, then a dual stage is the way to go ) is a good idea. Especially since the temp dials on the Stealths are good for a "ballpark" temp at best.
You should measure the temperature in the display tank, preferably in the middle of the back. The surface can be warmer due to heat from the lights.