pat, you are probably wise not to buy a 928. they are great cars don't get me wrong, but unless you are prepared to put a lot of money into them and not get it back when you sell i'd stay away.
951s are great cars too and should be a lot cheaper to maintain. they are pretty fast for their age as well. cheaper to buy and maintain than 911s but easier to drive and just as fast. aftermarket stuff is available to really make them quick, but can get pricey. look for 1988 Turbo S or 1989 Turbo models if you can. they have the best stuff and most power but are usually more expensive.
1987-88 944S and 1989-92 944S2s as well as 968s (all 16 valve cars) have decent power for a na motor, especially the later 3 liter ones. I feel they are just as reliable as the 944 if you keep up with maintenance. there are more things to break when things go wrong though (timing belt, tensoners). 968s hold thier value pretty good for a 4cylinder porsche but have the most power and latest technology. S2s are also more desirable. S models are only slightly more powerful than 8valve 944s but are still fun cars.
1987-88 924S models are basically a 944 with a narrow body. it also has the early dash which you don't like. cheap cars though.
1985.5 and later 944s and 968 have the later dash. 1988 944s had more power than earlier ones. the 1989 944 had a larger displacement motor.
early 924s and 931s (924 Turbo) are like 928s. unless you really like them, i wouldn't put my money into one because you will never get it back when you sell. that being said, my first porsche was a 1980 924 and it was my daily driver for 2.5 years. it was pretty reliable and cheap. of course i was working at a porsche shop, so i had experienced people making sure i kept it going. it was still a fun car, pretty slow though.
if you ever want to chat about these cars let me know. i don't know everything, but i've owned a few and really enjoyed them.
