2 comps and a sub box (approx 200lbs) on worn out sprngs in back......sounds like you answered your question there. i put about that much in my csvt (in good shape) coming home from costco and the rear was not happy. only did that once.
less weight and new springs, even stock might help alot imho

00 black/tan svt, #2052 of 2150, born 2/1/00 formerly known as my csvt "Nothing in the world is more dangerous than a sincere ignorance and conscientious stupidity." -Martin Luther King, Jr.