Help me select the right warming filter

What warming filter for color film will be sufficient at high altitude (Colorado) while remaining acceptable elsewhere (81a/b/c?)

The differences amongst the 81 series are pretty slight. The big jump is going from 81 to 85 series.

I used to be a big fan of warming filters. Especially with Provia the color pallet was much cooler the the old Ektachrome VS, which was my favorite. But I have begun to embrace the native pallets of various films and have cooled on the idea of warming filters.