Well suspentions are differnet animals for stait line vs curves.
in the curves you want no bind, free moving, positively locating suspention.
in a stait line you want less wieght, strong, good wieght transfer.
my .02
on your budget forget coilovers they are $$$$ that you don't have to spend. they are nice for ride hieght but unless you are auto x or something proably a bit of a waste. springs are cheaper for changing them out but most people are going to find a rate they like and stick to it.
get the MM drag rear control arms with spherical bearings. this will help locate the rear mor positively and reduce the need for a panhard rod alot. a panhards rods sole function is to locate the rear from side to side under load. these are kind of dual purpose purchase. use you subframes. get some nice shocks and struts. tockico, bilstein, koni
you already have springs make sure they are what you want to run. a good handling spring is going to be a trade off at the strip. a good spring at the strip is going to be a trade off handleling.
CC plates. these are a bit nice as if you get a spherical bering the strut is positively located so it does not mess with you camber under load. you camber setting has alot to do with you handling as that will inpact how much of the contact patch stay's on the surface.
I will say that the parnhard rod, torque are setups by griggs and mm are nice but it raises the budget sky high.
now all this being said if you want to go in strait line only. buy nice cheaper rear control arms with poly busshings. ajustable shocks and some soft springs.