Ok, not a really bad list. Especially the suggestion of a Nissan Z instead of a trouble prone 944 Turbo ('cause I have 944 Turbo that I bought new) that can cost more than the Z in the first year of ownership. Those cars need LOTS of attention, all of it expensive, and all of it by calendar time, not miles. Only 3000 miles on the cam/balancer belts? Well, if it has been more than 5 years,
better do the replacement, because the belts break... and bend the valves, and you will be into a $4000 repair in a heart beat. Don't get me started on the electrics, exhaust system, turbo water pump, dash cracks, upholstery, or the HVAC system. While you might be able to get parts or tech help from your local Porsche dealer for your 911, Porsche dealers don't even have anyone working there that were even born when the 944 Turbo was sitting on the showroom floor. They don't have parts. Not even an oil filter. Seriously, they don't want to see you. While the 944 Turbo is a great car when everything is screwed down right, it's a nightmare to service and maintain, and the prices are insane. The Z is actually faster, handles as well, and is perhaps built better.
You might even consider a Chrysler Crossfire if you want a two seat coupe.
A Cadilac CTS-V is certainly a nice exchange for an expensive BMW M5, but the Caddy is still expensive. The holy grail, a CTS-V wagon with a 6 speed manual is actually quite a bit more expensive than a nice M5 of any year.
What I have learned is the you buy what your heart wants. Buy it new, if you can afford it, and keep it. That might be a better deal than one of these "plan B" cars. If you have a "plan B", make sure that it is something that is on your serious list. Do your homework, drive the cars, look at everything. Eventually, what you want (within reason) will turn up, in a condition that you can live with, in a condition that you can deal with.