So i guess it doesn't have any relation to my car shaking at or around 55mph? It only shakes around this speed (and during harder braking), would this be a balance issue? I thought if your wheels were out of balance it would vibrate in and out as you go faster (like at 20, 40, 60, 80mph)?

 

If you go with cheap rotors, just save your money and get your stock ones turned. I would suggest some decent drilled rotors. I don't know for a fact, but I have heard that driving thru water or car washes while your rotors are hot can warp them too. IDK if it's true, but it sounds plausible.