Yes, you're high. Why would you sell a pristing M3 convertible for another convertible? I could see selling it to get a car more suitable for daily driving, like a sedan, SUV, something with a hard top.
Why do you think you'll daily drive the 135 convertible when you're not doing it now, with a car that's basically the same? The M3 is exactly the same kind of car, it's a convertible, it's rear wheel drive, it has a small back seat and trunk as the 135 convertible, nothing changes there.
If you have the itch for a new car and want to scratch it, go for it! Logically what you're saying makes no sense though.
'98 M3, track beast
'06 Porsche Cayenne Turbo S 521hp daily driver
'07 KTM 990 Adventure