Biggest mis-conception about coilovers are that they are just there to lower the center of gravity.

Yes, they lower the center of gravity, but most importantly, it gives the driver the opportunity to adjust the corner weight of the each wheels to achieve a balance in a car.

if you plan on just drag racing, I would just stick with progressive springs, but if you do a lot of mountain runs, and track racing, i would suggest linear setup coilovers and weight each corners to balance it, so it'll handle very nuetral at the track.

Or you could set it up as how you want your car to run at the track. This is the advantage of the coilovers that you can't get from springs.

and don't do the sleeves, they're not worth the money because you're using the stock strut setup that can't adjust to lowered spring rate.

good luck.