the speaker, factory uses weird ohm ratings alot of times so if its blown check out the back for power and ohm ratings and try to match it up. best sounding thing because of the weird ohm ratings would be a amplified tube from sonic electonixs and hook the high level input from the rear full range speakers to it. the factory uses filters in the amps and it messes up the sound of alot of aftermarket amps, so its best on the multi speaker stuff to stay all stock or all after market. thats why you need the all in one hooked pre amp to sound right.
2 take the door apart and use a meter to see if the actuator is getting the power from the switch
1998 Bonneville SSE
2007 Monte Carlo LT-KYB, Clarion, Polk audio, Kicker
1999 Yukon SLE-KYB, Air lift, Reese dual-cam, Tekonsha
1987 Firebird-355/th400-nothing stock