Thanks for the advice guys. Sounds like Miata is the overwhelming top choice. It was actually my first choice as well...but then my mom got an SL400. After driving that a lot this summer, my Mazda 3 feels really sluggish -- which is worrisome since, on paper at least, it does 0-60 in roughly the same time as a 2012 Miata.
Does the Miata really feel much quicker than it is? I don't care about the actual numbers or winning drag races; I'm just looking for that visceral thrill of acceleration
I definitely don't want to buy a car solely for its fun factor and then end up bored by it.
Responding to a couple other replies though:
This is the first car I'll buy outright for myself. I split the cost of my true first car with my parents and sister, so I don't really think of it as mine.
College and rent is fully paid for and I have around $10k saved and will make another $10-15k this summer plus a couple grand a month during the school year, so I think I'm in a place financially where I can safely afford either car. I just want to make sure I make the right choice, since this is far more money than I've ever spent on anything.