At the moment, I am running L7 subs and mids from stereo. The stereo has direct sub drive which I used to run the underseat sub. Definitely a marked improvement over the standard stereo.
Mods so far: 20" LM reps, Eibach Sportline, LCI tail-lights, LED H8 angel eyes, black grille, Black BMW badges, CIC/Combox/Bluetooth/6FL/6NF/6NR retrofit, rear headset monitors and PS2.
Awaiting iPhone 5 music/media snap-in adapter.