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.
'89 Porsche 944 Turbo LS1
475hp track beast
'03 Audi allroad 475awhp daily driver
'03 BMW F650GS Dakar