There are also places you don't want to go with a 928 and a DD gives you options. Mall parking lots, Places with lots of speed bumps, bad roads, bad neighborhoods. These are flagship Porsche cars from the 80's. They cannot haul a load of hay or take 4 adults in comfort. 928 owners are a fringe element amongst Porsche owners, and we all know what THOSE people are like...
You might want to "ease" into it with a 924 or 944. Sure, they aren't quite so neat, but, they are good training. Once you want more...you can go from half an engine to a full engine.
What do you like to do? I mean...What do you want to spend time fixing? Sooner or later you will have to do pretty much everything. How much time do you have? Garage space? Tools? What is your favorite Fuel infestation system? AT or stick? what is your favorite engine? 16 v 32 v? Displacement? Does AC really mean a lot to you? How much time do you have to devote to the car? (please note the word "devote", it is NOT accidental) will you be looking for a great paint job, or crawling under the car and looking at the engine first?
DMRK: I just did the HCore on my 924S, Darn that heat is good! The AC is Ice cold too! But, we are talking 928 here. Twice the engine, twice to 10 times the cost, twice to 8 times the difficulty, and about 3 to 6 times the Porsche reverse economic ratio (PRER). YMMV.