just saw your other thread. you were asking about eibachs and having a system. in the rear of my 4door hatch, i have a JL audio 300/4 amp, a Jl audio 250/1 amp, and a sealed dual chamber 3/4 in MDF box with 2 JL audio 10w1s. the whole back of my aveo vibrates, but the eibach springs dont stiffen the rear no where near enough to mess up audio equipment. Now if you had a big system and had eibachs and went out for some WRC racing, you might have some problems LOL, more than the spring affect on your audio though LOL