Curt, wise move. I have a K250 and have never regretted the expense.

Don't know exacly where you are in the PNW, but out here in the Monroe/Sultan area (Spada Lake watershed) my ambient cold water temperature never rises above about 66-67F during the hottest weeks of the year. That means I have the luxury of perfectly tempered (68F) water available year-round. Beats the heck out of the darkroom I had decades ago in Southern California where the summer water was 84-86F.

My recommendation might be the 'D' model because of the preset temperature breakpoints that are configured to the commonly used photographic standards on the Fahrenheit scale. On the 'E' model they are set to even 5-degree Fahrenheit breakpoints only.

Note that the 'D' model has a setting for 68F, while the 'E' does not.

'D' Model
F: 65, 68, 70, 72, 75, 80, 86, 90, 95, 98, 100, 102, 104, 105, 115
C: 18.3, 20, 21.1, 22.2, 23.9, 26.7, 30, 32.2, 35.0, 36.7, 37.8, 38.9, 40, 40.6, 46.1

'E' Model
F: COLD, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, HOT
C: COLD, 12.8, 15.6, 18.3, 21.1, 23.9, 26.7, 29.4, 32.2, 35.0, 37.8, 40.6, 43.3, 46.1, HOT

Ken