Nate, you gots some serious research to do here.
1) your posts and questions in this thread have consistently shown you to be extremely concerned about every possible repair cost, the underlying message seeming to be that for you any repairs needed to a used car would be a huge problem
2) you have not even checked into the actual costs for you to insure a WRX??
wtf, do you have any IDEA of how much insurance would cost you at your age for "the worst car to insure" on the market??
my prediction is that insurance for you on a WRX could be approximately 1/3 of the car's initial purchase price PER YEAR. that's like $5000 on a $15000 used Rex wagon...that kind of money buys you absolutely nothing, besides being an insane waste of your mom's $$$.
Do you realize that $5k could cover a whole lot of minor repairs to an older car, which would leave you with something a lot more solid. I believe that if you really analyzed the numbers, the insurance difference alone between an 05 Rex wag and that 01 OBS would more than cover any needed repairs...and this just in the first few months of ownership. this does not include the substantial difference in initial purchase costs. Add up those figures, and your mom would have to be utterly insane to go along with helping you buy a WRX...unless she needs a huge tax writeoff or some other way to get rid of excess $$$ unnecessarily
in which case I will write her up a proposal to sponsor a certain well-known rally team instead of buying you a car!
and Gawd help her checkbook if you got ONE ticket with a Rex, then you would go into the Assigned Risk insurance pool at something like $1000 per month, right up there with the 5-time DUI losers, deadbeat dads and ex bank robbers.