OK, car guy here (ask me about my StupidCar).
First, I think you are ignoring hedonic adaptation. This is not a one-time car purchase. Do you really think you're going to buy one, say, $40K car now, and then keep it for the next 40 years? Not the way these things work. Once you are in a car that's really fun to drive, you are not going to want to go back on pain of death. That means that the longer in life you can postpone getting on that treadmill, the better off you are, because there are fewer replacements to factor in, and fewer fancy new things you'll learn you now desperately want. So when you figure out how this will affect your budget, factor in a replacement fund, too, assuming you replace the vehicle every 5-10 years for the rest of your life.
Second, your plan is reasonable for where you are now. But does where you are now reflect where you want to be in 10 years, or are there changes that may come? Is there a partner involved, or a potential partner in the future? What about kids? Do you own a home, or might you want to at some point? A sportscar is the best embodiment I know of immediate gratification -- it is like the best BrightShiny EVER. Longer-term goals often feel less urgent/compelling in the moment, but they can actually make your life happiness significantly better or worse depending on how prepared you are.* So make sure that plan accounts for changes that either you might like to see, or would really hate to have hit if you're not financially prepared (e.g., the hit-by-a-bus outcome).
Then do the research and the actual math. Call your insurer and get a quote for the kind/year car you're looking at. Think about various options that might be fun to drive with less outlay (a used WRX comes to mind -- driving that car made me bust out in a grin). Use IRS figures and anticipated mileage to figure out likely depreciation and maintenance costs -- then double those if you go upscale (funny how maintenance tends to increase dramatically with car make/model -- I have a 911, and OMFG).
Then, since you don't have a clear vision of your dream car in your mind, give yourself a year or two to do real-life research. What is it that makes you smile? The pedal-to-the-metal acceleration? The growl of an engine? The handling through a tight turn? Are you big or small? (We looked at the Alfa sports-mobile, and our American asses barely even fit in the seats; I ended up not getting the WRX because my DH's hockey-player-build shoulders weren't comfortable; etc.) Do you want to attract a lot of attention or fly beneath the radar? The idea of a sporty feeling means different things to different people, and the only way to figure out what really resonates with you is to try out a bunch of different ones.
Once you have a whole bunch more data and a better sense of what matters and what doesn't, look for the car that represents the knee of the curve -- the one where the smiles:price ratio is highest. I've always liked smaller cars that are zippy, with a stick, and with excellent responsiveness/stability around turns, so I'd be much happier in a Miata than a Camaro, you know? My DH is exactly the opposite -- he's all about big cars and pickup on a straightaway and has a thing for American muscle. There's no right or wrong,** just the best choice for you.
FWIW, my own path: I always had cars that were fun to drive but clear daily drivers, not a "sportscar" per se (e.g., 1990s Acura Integra GSR). Once I had retirement and kids college fully funded, however, and I could pay cash, I did let myself buy my dream used car (2015 911 Carrera 4S GTS Cabriolet -- turns out having the top down makes me super happy). Actually, I let my spendypants DH talk me into it, but same difference. It is far and away the best StupidMoney I have ever spent in my life; I literally smile every time I drive it. OTOH, I was also in my 50s, and the kids no longer required a back seat, and like I said, we were already FI, and I was still working just because I wanted to. And I DO consider this to be my last car, because I'm old enough now that it's feasible, and it's the kind of car that people really can and do keep 20-30 years.***
Part of the reason I enjoy the car so much is because I DID wait. I get nauseated about spending money (almost threw up buying the house, no lie), but there was no guilt or stress here, because I knew the future was covered, so I wasn't putting my own fun above someone else's (or my own) needs. I worked a lot and saved a lot for a long time, so I really have a feeling of having earned that kind of a splurge through my own 30 years of delayed gratification.
YMMV, of course.
*I am reminded of my buddy who went to Harvard Law, graduated with $100K in loans, and then realized after a year at BigLaw that he absolutely hated BigLaw and wanted to be an FBI Agent. The next 5-ish years for him were NOT particularly happy.
**I lied. He's wrong, I'm right.
***It will certainly be my last car for as long as I can drive a stick, as those are few and far between. Assuming I don't do something stupid with it first. And part of the reason for buying it at around 50 was I was starting to get periodic left knee issues that made it clear I might not be able to drive a stick forever. Since that is a key part of the experience for me, DH pointed out it made sense to buy the car while I could still enjoy that aspect of it.
