Don't get anything with too much power, or too sporty - the insurance payments will kill you. Don't get a $25k car - the insurance payments will kill you.

Suggestion: Get a 2-3 yr old car (let someone else take the depreciation hit) that is nice and "family-oriented" (i.e. either 4 door or a hatch), and something that has large aftermarket support (lots of aftermarket parts available). Once you get the car, you will get bitten by the bug to midfy it to your liking. Rims, stereo, suspension, etc.all cost money. Figure out how much you plan to spend on these items, then double that figure, and that will tell you what you really can spend on the car to keep it within your budget.
Example: If all of the accessories that you want for the given car add up to $4K, then double that to $8K. Take the $25K that you can spend on a car, subtract the $8K. You can spend up to $17K on the initial purchase of the car.

You might want to stick with the basic cars to start with - Civic, Scion, Jetta, etc. Stay away from used Supras, RX7s, etc. Parts and labor are much more expensive for high-performance cars, and insurance will kill you on them - if the power doesn't send you into a tree first.