Deals are out there to be had especially if you are willing to travel. I got my 11 gt vert for 26500 with 23k on it which is a great price for a vert. Only problem is i went 900 miles to TX to get it. That being said your budget of $25k'ish is reasonable, especially if you find a motivated seller. I'm gonna bullet a few points for you as its probably the easiest way to do it.
-You want an 11+ car as 10's still have the 4.6
-The performance option for these car's in 11 is the brembo option which includes brembos, wheels, and revised stability control. I think it includes 3.73's too but i may be wrong. I'm thinking a guy of your age you might not need or want the brembo option and will be happy with a premium car.
-Cloth sucks so opt for a 400A or 401A car. The stripe in the 401A car seats comes in different colors.
http://forums.themustangsource.com/f726/400a-versus-401a-leather-485297/#post5909009
-I would opt for a 3.55 or a 3.73 car. It's not the end of the world if you get a 3.31 car as gears are a relatively cheap mod.
http://www.latemodelrestoration.com/products/10-14-Mustang-Rear-End-Gears
-Manuals are nice unless you plan to mod heavily (which i don't think you will) then i would say opt for an auto.
-Get a premium package car. This will add bluethooth, XM, Sync, leather, power driver seat (optional passanger), 500 watt shacker radio, optional heated seats, beefier steering wheel, multi color ambient lighting, there is also a glass roof option, etc..
There's probably some stuff i forgot and some stuff i got wrong but i am sure others will chime in.