First off, good man for realising you need to do something. Second, don't be an idiot an get another performance car as it'll either be fragile (rx-7, GTO) or too tempting to spend cash on (anything big with a turbo on). Get a shed so you have no temptation to spend money you don't have as it's pointless, or get something cheap and cheerful that won't have big costs (mr2 again, or mx-5?).
If you're in that much trouble you have to sell your car, then buying another fast one is just daft. Don't take any of this the wrong way, you know I love you and that, but I don't want to see you take a bad turn on this one fella.