I have a 93 240 coupe

Was wondering what is the best and cheapest full coilover suspension to get cuz imma keep the car till it dies....which will be in a few years so nothin too drastic is going to be done. I don't want to lower it too much either, only like an inch.

Also, i've been getting this weird sound at about 3000 rpms. Its at every gear. Its like a rattling, like the fan is hitting something or something. Its like that sound you get when u put a baseball card in the spokes of your bike when you were a kid. Anybody know what it is or what i can do about it?