well, not a lot, as its a small system, but lets see
HU>stock $0
Front speakers>stock $0
Subs>2 Resonant Engineering RE8's in 1.5cube box tuned to 35hz, $175 for all
Amp>Jensen XA2250 , shipped to me for free $0
New amp coming soon to replace POS Jensen>PG X400.1 $135
4gauge wiring kit>$45
all installation done by myself>$0
grand total $355
and metered at 131db on dash @40hz, and 133.3db in kick @49hz
not the best , not the loudest, but I'm very happy with it
wooops better add on Weatherstripping around the trunk and under the license plate, whatever thats gonna cost, to stop the vibration noise, but I haven't done that yet