When can I afford a “nicer car”

For context I’m 17 and have around 17k in Sharesies (was a bit higher but volatile market) and almost 5k in a hysa as an emergency fund. I don’t really have any expenses and that and shouldn’t have too many going into uni. Im hoping for near 70k invested by the time I graduate university. Have run the numbers and been harsh on myself, assuming everything goes well this could be upwards of 80k. I want to eventually to move this investment into real estate but I don’t really see myself buying a house to live in until I am ready to have a family as I don’t really know where I want to settle down for the rest of my life, and certainly don’t think I will after uni. With all this considered, I drive a shit box and intend on doing so for a while. But when can I justify buying a car for 20k? Something a bit nicer and sportier, still used but just a bit nicer. Also do I pay it off in cash, or if I can gain better returns reinvest the money into real estate/shares and take a car loan out. This is something that’s got me really thinking and would love some advice. I know car debt is typically viewed as negative debt and for good reason. Thanks!!