Great to hear! Heat is a concern everywhere unless you happen to live at the poles. I would recommend the 1050 or 1050 Ti card, if you want to keep crunching GPUGrid. They're efficient and won't put out the heat like the big boys.
I don't know what projects you like best, but all of those cards should work on Einstein and SETI, and probably others too. GPUGrid just happens to be one of the more demanding projects. If you ever decide to upgrade just make sure your new card fits, sometimes those Dell and HP cases don't have much extra room.
There are plenty of projects that are CPU only, don't feel like you have to crunch GPU projects.
Decision Reversed Again: I purchased and placed in service two GTX 1060s last evening and obviously productivity jumped solidly as did the room temperatures. The previously mentioned GTX 550ti and GTX 750ti never downloaded a single task. The GTX660 is successful but requires over 20 hours to complete long units. Again thanks for the inputs and support.
Another casual comment: I will acquire a new DVI flip switch as the new cards do not permit crossover to the VGA from Digital; but no problem. Obviously my monitor permits both. Bill