DEAR SIRS, I AM GETTING READY TO SELL MY TENTEC #425 LINEAR AMP AND WAS WONDERING AS TO THE VALUE OF IT. IT IS ABOUT 10 YEARS OLD IN PERFECT CONDITION WITH VERY LITTLE USE. I KNOW THAT THE NEW UNIT SELLS FOR ABOUT $3500 AND ISN'T OF QUITE THE SAME QUALITY AS THE OLDER UNITS. WOULD YOU HAVE ANY IDEA AS TO THE VALUE OF MY UNIT? THANKS, TED