minimax

Ugh! This is going to be  a bit difficult. What is a Watt? What is an Ohm? a 50 Watt output might be about 10 Watts RMS, the only proper measurement. 4x22Watts is actually almost indistiguishable from 4x50Watts  as you should know. Assuming a modern class D amplifier, you will be drawing four Amps at least from the supply at 12 Volts. If you are running off a bench power supply, it will need to be adequate. Are you running into the correct speaker impedance? Have you taken the door cards off  and the T-bar cover likewise and checked the condition of the speaker cones? I have often found them to be pretty tattered. How are you measuring the distortion? Bruel and Kjaer distortion analyser or a scope on the speaker leads? What are you using as a load for these checks ? What is the signal source? Signal generator set to line level?  I doubt VERY much if there is anything wrong with the Pioneer kit. I use it myself in my car and it sounds fine. If your battery is not going flat then the  voltage is correct anyway. Why do you think that something is wrong?  If you are getting distortion, you have either poor speakers or poorly made power connections. The nominal alternator voltage will be over 13.5 volts at the radio's power terminals with the engine running.