I know 3 Drivers that have Magnums 1 is a s-3 another a s-6 and the other is a s6-80 and all sound great and all have been tuned by somebody that KNOWS magnums and they have had no problems! Therein lies the problem Most of your "Golden Screwdrivers" behind the truckstops in relocatable trailers don't have a clue how to work on a radio unless it is a Cobra or any of the lines that have connex boards in them! Take it to a reputable brick and mortar shop that has been around longer than 5 years and you'll probably find someone that can properly work on the Magnums!
I have a General Lee that does between 50-60 watts anybody that says they will do 70 is full of it and you should run the other direction without question! It is a great no frills basic powerhouse!
Just my .02