Of course I will have to disagree on the Delta, it's not that I dislike them in any way, it's just the potential problems you will run into are much more present in Delta thermostatic valves. Stay away from Kohler whatever you do I will say that. If your going for cost wise then yes Delta is the way to go, but I assure you with thier limited warranty you will run into some "obstacles" later on down the line. You pay the money for the best you get the best. To be perfectly honest with you Moen doesn't make something cost effective for what you want so I would in this case go Delta for what you ar asking for.
And the gentleman above is 100% accurate, you are going to be paying for the thermostatic aspect of the valve, they are the most expensive because they are pretty much what's the top of the line now a days when it comes to Tub/Shower or Verticle Spas when you throw in a transfer valve.