If you buy a car you can't afford yet you're an idiot. when i was a boy (many, many years ago) my Dad said, "never buy anything you can't afford to pay in cash for twice over." And obviously he's my old man, so i'm always going to agree with him, but he has never ever been in any debt. And following his example, i haven't either.
Living beyond your means is stupid. Why would anyone ever want to create a massive financial hole? It sounds to me like you're losing motivation and you need a big reason to get motivated. It sounds like you're going through a similar thought process the guru-buying-wannabe goes through when paying for a $2k course. If i buy this, it will work...
Perhaps i'm completely wrong, so maybe you buying this car is not so much a motivator, but a means of showing you've made it, why else would someone who can't afford a car like that buy it?
I would say you should go in that dealership, and look at it regularly. Let the staff know you can't afford it, let them treat you like a cunt, then when you have the money, buy it. But DON'T, DON'T be stupid and do it now.
If you wanna think about buying a new car because you believe it will make you look and feel the bollocks, as well as be motivational, i'd suggest you're simply employing Cialdini's confirmation bias. You're convinced it's gonna change shit. It won't. Not for the better anyway.