[TSM330i]

Don't even look at an AM. Everything I've seen from long-term owners has them pegged as a POS. I drove a DB9 Volante' - it was a joke. The build quality seemed like a bad kit car at best. Compared to a Gallardo, it was horrible.

Cars are truly bad "investments" unless you got in on the ground floor (like the 1M or the original Ford GT from the 2000's).

That being said, it looks like you're more interested in something that could hold onto its value and retain the most value - and a bonus would be an increase in value long-term.
R8 with a manual - the later cars with the V10 and a manual would be stellar for sure.
Gallardo with a manual - not as bad as you'd think for maintenance - again, plenty of sources out there to figure out what years are good.
Viper can be a fun car, however, I'm not sure they'll go up in value. I think it'll level off at best. They just didn't sell well to start with so it tells you something right away. Not that many people wanted them.
964 or 993 - have been holding steady with prices, but they're pretty high. Not sure if they're moving or not at those elevated prices
997 - I think you missed the boat. The prices have gone up quite a bit and are holding pretty high (a nice car is around $60K!)
997 GT3 I would think is the best of the bunch. You can get them for under $100K and it will last. It has a manual transmission to boot.