never look at wattage, and sertainly don't compare with pc-speakers.... those 200watts are just a figure..... might get 5watts out of them.... a car is absolutely totally different to a room. My install is verry modest, even for a pure SQ-install.... I'm running around with 400Watts RMS, and that's about ok for easy listening.
You see: subs need a fair amount of power to produce the low frequencies.... Thinking 400Wrms is overkill in a good soundsystem is wrong.... Also, if you want SQ there's far more important things than speakers and amps.... you could roll with speakers and amps for about $400 total, but the far more important things are good wiring and damping in a SQ-system and prepare to pay easily as much on that!!!!