yeah, Carmax will buy your car no matter what as long as the title is clean, and it's in sound mechanical shape. they have already made me an offer. if the car has too many miles for them to sell, they will turn and sell the car to a wholesaler. They then usually auction the car to the highest bidder. The car then finds its way to some private used car lot.
As for Porsche parts being too hard to find

, There are a ton of website for performance parts for all the watercooled porsches 944/924/928/968. The 944 is a big item, there are all kinds of goodies on the market. They do cost more to maintain, but I doubt this car will see more than 2-3K miles a year. You can get engine packages from 290hp all the way up to over 700. Just depends on how deep your pockets are. I'm happy the way mine is.