I stretched and bought a new K250 ten years ago. Absolutely, positively the best darkroom expenditure I ever made. There is nothing like pressing a button... and instantly getting perfect temperature water. Every time. Over and over. For the rest of your natural life.
Mine is so precise that I when using water jackets I routinely adjust by 1/10ths of degrees to account for heat gained or lost to the environment from SS holding tanks. There is no slop. There is no error. Perfect every time.
The only caveat might be to verify in advance how many weeks each year you can count on a sub-68F ambient cold water supply for mixing. Or whatever temperature you use. This will tell you how many weeks of use you can expect annually. Fortunately for me in the Pacific Northwest, my ambient cold water is under 68F year round. But YMMV...
Or if you live in the Southwest where the water temp is seldom that low, you can buy a chiller. My water comes from above ground tanks and much ofthe year it is pretty warm.