I drove and owned these cars when they were new. I still have a Porsche 944 Turbo, my Mom's car, that she drove for 35 years. It's very original, and we have had lots of experience maintaining it... Which is why it doesn't impress me much. The 968 is actually a far better machine, and easier to maintain, so good pick.
The Dino is fabulous, but you need $300K to open the door, or more. And then, what do you do with it? I'd love to have one, but... How much fun could I have? I went through this with my R5turbo when it entered 6 digit territory. No more flinging it through the canyons with its flawless original paint and hard to find tires. Every corner entry had the thought "100K+"... So now I restore them for others. 'Bought an early Morgan +8, figuring that it will appreciate enough to send my young daughter to college about the time she takes away my keys. I am having a lot of fun with that.
The GTO and the Cad are still the same barges now as they were then, only more expensive, and likely not as fast as any modern sedan with near 300 HP. The workmanship and handling really didn't do much for me, and most of the restored versions I have driven only bring back to mind all the reasons that I didn't buy one back when they were new.
Land Rovers ae special, because they are properly focused, and very specialized. Parts are available and they don't require the care that, say, a Dino or a primo GTO would. Park it anywhere. It will never be painted in some custom color that can't be patched should it get a ding.
I owned a couple of Volvo Turbos, and they are great fun. They steer well, and can handle quire well with a set of proper tires and dampers. There was a factor boost kit for the 700 series cars, and the gearbox was a wonderful thing to shift. If you tire of the 4 cylinder, you can put a Ford 5.0 in it, or a Chevy LS3 with a 6 speed. Why not? And they are practical, with available parts and plenty of knowledge to keep them running.
The Mazda is cool, but hard to find a good one, which will drive up prices... So look for a good one now. Same for the Suzi, which fits more into the Land Rover mind set, but cheaper and smaller. Would make a good book end to a Land Rover collection.
I don't want to rain on anyone's parade. I am old, and have a pretty good memory of what I liked, and what I still like today. Thinking about what would be cool to have in 20 years... How about a Chrysler Crossfire? The Subaru BRZ/Toyota would be pretty nice to have. Miatas will always be good to collect, just as TRs, and MGs are today. Fox Mustang 5.0s are going to be a good bet, as they have lots of good parts available, and can be built into very impressive track cars with careful parts selection and development. There are also quite a few HP increases that don't run afoul of the emissions laws. They are still relatively cheap. If you can't afford one of the rare Saleen Fox cars, you can build something better from a parts catalog, in your garage.
