GB1,
As Bret said, take a look at my sig pic. Yes, I owned an '84, and it was a very good, solid car.
I've had a bunch of friends with 928s, and yes, two had some electrical sensors go out along the way. One (the test car in my story,) was extremely reliable.
My father had two law partners that bought 924s new. They were reliable compared to the Audi 5000 my father bought -- just too underpowered.
The 924 Turbos are decent cars, but tend to be abused. I've had chances to buy at least two well-running, solid examples for under $1000. There's just no market for those cars!
924s will never appreciate. 944s will eventually come up in value -- especially the Turbos.