i got jl tr600-cxi in the front and jl tr690-txi in the back, these were hand me downs from my brother. Thing i am wondering is would i notice a huge upgrade on lets say $250-300 components?
The biggest difference between a coaxial and components will be your midbass. Running Coaxials off a HU gives you literally no midbass while components wired to an amp can give you awesome midbass. The Sq in general is better with components as well.
Components allow for a MUCH better soundstage (Higher, and you have more control over it). Usually much better frequency response, handle more power usually, and like already mentioned midbass is much more pronounced.