The 50x4 rating is peak, not RMS. It will only produce the 50 watts for a very short period of time(usually less than a second). Reputable amplifier makers will rate their amps in continuous power (RMS)using (IIRC) the EIA-J standard. Companies like Rockford even include a tested power output for that amp. Kinda like a dyno for your amp! Remember, not all HUs include an amp, most high end units are pre outs only!
To get back on topic, a system is only going to sound as good as it's source. Feed speakers crap, get crappy sound. Start with a good, clean source, then work your way up from there!
