Chevy Cobalt or a Nissan Skyline?

[DriveTooFast]

Right now I own a 1998 Grand Am GT, it's a great car for its age and really reliable but I do want something with a little more punch when I step on the peddle. My friend is able to get me a Cobalt or a 1995-98 Skyline for under $3000, but I'm not sure which one to choose.
It comes down to I don't know which one has more potential for upgrades and speed/handling. I need some facts to help me make this decision.