I think a lot depends on where you live. The constant ground temperature will keep your water temp from large temperature swings, but is usually too cool for tilapia. I use the cooler ground temp to keep my water cool, both summer and winter in Colorado and have success with trout.
Channel or blue catfish are very good option. They are more cold tolerant and are very hardy fish and besides good to eat.
Figure out what species grows naturally in your area and go with that species. We are in Trout country here in NE TN and we raise trout with very little input in our AP system that ranges between 45 and 70F. Catfish would do well here as well but handling them is almost dangerous due to the spines and chance of infection. Not to mention the salmon family (trout in our case) is so delicious and the oils are very healthy.
Jim, I'm curious, given your temperature range, are you using biofilters? I was thinking about the bacterial activity, and its slowdown in cooler weather. I love trout and am going out this weekend to try and get one or two now the ice is off the lakes.
that trout looks yummy Jim.
the new system I finally got around to starting has a HUGE cistern. to the tune of around 8'-10' across and 14-16' deep. seriously thinking of using all that cool water storage to grow a colder water type of fish in at least 1 tank. I was thinking Crappie but trout might work too. I figure I can adjust the flow into and out of the fish tank to get close to the ideal temp I want (more flow in the heat of summer for instance)
I already have a big farm pond stocked with channel cat so I prob wont use them in this.