2006 Chevy Impala, 150k miles, $3700. (No idea yet if it has to all be up front or they accept payments, calling tomorrow)
2001 Ford Mustang GT Deluxe, 90,000 miles, $3500 [Again, no idea if all up front or payments].
While that 2001 GT definitely looks tempting, I don't think I would recommend buying another 17 year old Ford. The Impala should also be a big no, because I've known way too many people, my sister included, that had a ton of problems out of the Impalas from that time period.
You say in the thread that you're not really a car person, so you should really consider just buying a used Japanese car with somewhat decent miles. If you can bump your budget up just a little more, you should be able to find a very decent Civic, Corolla (meh), or even maybe an Accord. Compared to a Chevy/Ford, you may pay a little more for the same year, but you will most likely save in the long run. That's not always the case! You could buy a Honda that blows up in a month and a Ford that drives for 30 more years, but the odds aren't really in your favor there. Also, I am fully aware that this is less of an issue nowadays, but I do feel like American manufacturers were still working through some issues for the models that OP would be looking at.
If you still want something a little sporty, then maybe consider a Honda Prelude. They stopped production in 2001, but they were really nice little cars that rode well, but were also fun to drive. Your only problem will be finding one that hasn't been "riced out" and driven into the ground. Also, the automatics had a lot of problems, so only consider this option if you can find and drive a Manual.