ok, made up my mind.
got 2 Alpine 750W 10" subs 4-Ohm
Kenwood 500W, 4 channel, 4-Ohm amp, bridged to 2-ohm, 2 channel (no clue on bridged wattage yet)
Sony X-Plod headunit
replaced the door speakers with 2, Bolt 180W 6.5" full range speakers
and a 2 farad capacitor (undecided on brand, didnt buy it yet)
lets just hope that the system and my sliding rear window play nice together