Help understanding Stereo Power

A quick primer. You said you have 4ohm speakers. Ck the spec sheet of the head unit and you will find output with THD listed. I just finished my 03 Santa Fe, my wife would not let me have a new truck, and I started out simple. Use the OE amp with a new head unit and 2 sets of 4 ohm 2-ways. I could not get rid of the alt whine with this set up. Threw the factory amp out, a Monsoon, and install an MB Quart 90W, 4 channel for a UTV. The amp was $60.00 online and MB makes great stuff. The reason for the small amp is the lack of space in a Santa FE. New direct power to the amp from the battery and then up to the head unit. Whine gone. The sound is much better but not quite right. Memphis Audio 2.75" midranges added to the front doors. Still not happy when the dog is in her kennel in the back and I am running just the front doors. Change to 3.5" DS18 in the front doors and moved the 2.75" to separate pods in the rear. I now have 3way front and rear crossed at 1975 hz and 15.500 hz. Sounds great and just needs a little more EQ adjustment. Be careful what you start as it most likely will snowball. Most aftermarket head units will provide you with 40 watts power and should be good for your application. For around $150.00 you can get almost any name brand with a 10 to 13 channel EQ. If you do not want bluetooth capabilities you can find a good head unit for around $100.00