hook- I'm familiar with a few of your choices...let's see...
Air cooled VW's- Not (*IMO*) fun to drive, but many do some people love 'em so decide for yourself. If you're not buying for the driving experience, the *rest* of the experience sounds right down your alley- easy and cheap to work on, cool styling, great support network, classic time-frame aura (the whole pre-1980s thing just radiates from these cars).
Older BMW- Watch out for rust!!! Often they can't be saved, so this is just *critical*. Great fun to drive if you don't mind the bottom-hinged pedals on some of them. Great support network. Heh heh, these things are classics if you like the sport-sedan thing (which I do). Not always as expensive as one might think to maintain, but find a good mechanic.
Porsche 944- While some "purists" dismiss any front-engined Porsche, the 944 is a great car, period. Incredibly good-driving experience. Somewhat expensive to keep maintained though, but they do hold up well. Make sure you have a good mechanic check it out first, these can be *really* expensive if you get the wrong one.
MG- Get a good one. Fun and classic. Can be pretty reliable if you sort 'em out. Great support on these, too. I myself would probably get a Triumph instead though. Just a bit more classic, low-buck British sportscar in my mind.
RX-7 convertible (though I was thinking about the first generation coupes, my faves). Not all that pricey, certainly not compared to the 944. Watch for apex seals on the rotaries, it's usually just a "replace the motor" thing as opposed to a rebuild. But that's not as expensive as it sounds. Sorta a "baby-944", and I mean that in a good way. At least check out a few of these.
Nissan 300Z- A friend has one (actually a ZX, I believe, not a ragtop either) and it's held up well. I don't like driving it though, sorta like a 944/RX-7 with all the fun taken out.
If you like the origami-styling, the early toyota MR2s are cool, and the later ones are sorta like a Fiero (sp?) done right. Kinda "mini-italian" mid-engine cars. Some people *really* like 'em.
Oh, and the older Fiat convertibles are sorta like an Italian version of the MGs. Alfas are worth a look if you know a decent mechanic.
Notice how I kept saying "find a good mechanic"?
