Sorry to sound negative.
Your estimations are overly negative.
Any current recommendations on the most efficient solar panels, or is it such a slim difference it doesn't really matter as long as the price is good and it doesn't break ?
So far got lucky with $190 grabbing a 100watt panel which puts out exactly that in perfect sun.
When I was doing my research, I found that SunPower seemed to have better efficiency and warranty support than their competition.