its not just the extra weight that kills, its where the weight is- all the way in the trunk. so when you launch, its that much more weight transfer off the front wheels, so less traction. ill bet a big box in the trunk could easily add .2-.3 seconds to a 60' time, which is killer. if you gonna race, get that damn box outta there!
i dont feel like posting up every different setup i had, but i started with one jensen amp and a 10", then got a bigger amp, then 2 10's, then i got some sony 10's, then a sony amp, then my first fosgate amp, then 1 fosgate 12, then 2 12's and then like 2 other decks and finally my current setup. ive probably taken apart my whole system and put it back together at least a dozen times. its all good, i enjoy it.