No, you've got it. Get a DD Maze X-1, and you'll have the pelt. Just make sure you apply the necessary condensation prevention, and don't do it wrong either
As for the heatercore, yes, a car's heatercore is best: get the biggest one you can fit in your case. Mine's Fedco# 2-304, and is about 8" x 6" x 1 5/8". I'll be using a car's blower, to vent air through it (running at 7 volt, for silence). It'll be some work to mount, but it will work exceptionally well.