This is crazy...why on earth would you buy a high performance/luxury used car on a $25k salary? Aside from the facts that 1) there are ALWAYS unforeseen expenses on cars, 2) lux, sport, and used are all not great words to throw around when trying to minimize operating expense for the car, 3) insurance will likely kill you and 4) There is NO reason to have a $15k car on a $25k salary --
you're probably going to feel ridiculous if you do get a really nice car in this situation. I am fortunate enough to be making a little over twice your salary at the job I am taking when graduating in the spring, and would feel ridiculous if I kept my car and drove it to work. It's an 06 M45, $60k new, probably worth around $15k now. You don't want to be the guy at the most entry level driving around with nicer cars then people multiple levels above him. It'll look like you're trying to hard to be big time. When the expensive come around (and I have had MANY, and the M45 is by all means, one of the more reliable cars out there), you'll be killing yourself to scrape together a few bucks to keep the thing running. Get a $5-10k nice reliable ride, cheap to run and insure, and you'll have some $ to save to move out on your own and even some to spend on actually a good time. Last thing I would want is to roll around in a recent Benz but not have the $ to buy a girl dinner when I want to.
Just my $0.02. I know it sucks, but I'd just buy a basic Honda, Altima, Toyota, etc. Early 2000s Maximas and TL-S (mentioned already) are pretty quick and fun cars (for what they are). If you do some research and try to maximize the chance of getting a reliable one, they could be a nice, moderate step. I also wouldn't discredit the RSX. If you can find a maturely driven one, they're pretty quick and fun to drive while being very economical. On second thought, the type S only came in a 6spd on that one, so it might be out for you.
Best of luck