I'm always keeping an eye out for 70's and 80's 911's. Stock, unrestored cars are kings in the Porsche world. Cars with modded bodywork, especially slantnoses and updates (like an SC with 993 bumpers) are at the bottom of the price range, usually low to mid $20k's for decent drivers (which is fine with me since those are the ones I like). Funny how things turned out backwards in the Porsche world - a decade ago people would pay major $$$ to update their cars and now the expensive ones are the backdated ones. This one is comparable to yours and just sold today on BaT for $21k and though some aspects of yours are better (one-owner, lower mileage), I would say this one is a better car overall:
https://bringatrailer.com/listing/1979-porsche-911sc-10/