kind of a tough one...

[SuperSleeper]

Colin, for Christ sake, do NOT get another DSM. I realize this goes against this whole board, but it's a freaking death-trap, dude.
Knowing your mom, I imagine when she said "new", she didn't mean a 12+ yr old car that you'd rebuild completely. I imagine she wants you to get something reliable and good on gas mileage, and I personally think you want both those things given your life where it's at right now.
Here's my input: find something new to maybe 2 yrs old that still has some remaining warranty on it. MSP is a good idea... also consider Mazda 6, Ion Redline?, Scion tC, Honda Civic, used TL, etc. Something that's sporty, but still offers a reliability cushion. I'm sure you could find something in that area for around $700/mo for payments and insurance, assuming your parents have decent credit.