"For $5K you can do a lot:
Coilovers
Front and rear sway bars
Extra set of wheels with sticky tires
I'd personally go for something like this:
Bilstein PSS9 or KW V3 coilovers - $1,800
GT3 front sway bar with end links - $450
Tarret rear sway bar with end links - $425
Wheels - $1,000 used
Tires - $1,200 or so"
Ditto, if you have 5K burning a hole in you pocket, that is just what I would do. Even if you were not to track the car the suspension upgrades will transform the driving experience.
Ed