Suspension upgrades, atleast to me, is neck and neck with performance mods. I spent about 4k on my suspension. adjustable tien ha suspension, front and rear sway bars, front and rear strut tower braces. It handles better than my brother's M3.

As to if the motor has too many miles on it to mod...

Stick to bolt on's. Anything more and you might have serious issues...I wouldn't go forced induction without at the VERY least, a rebuild.