Well, I got rid of my 40 series and got a 50 series. From the place where I got my system, I traded in my 40 series and paid an extra 20 bucks for a new 50 series DELTA FLOW. I like it A LOT BETTER. I LOVED my 40 series, but I have been taking my boat out a lot lately and it is WAY to loud on the long trips and up through the mountians. So I traded in the 40 series for a 50 series and towed the boat today since I picked up the truck yesterday, and it was MUCH better. It still has a good sound when you want it, but itn't as loud towing and inside it isnt as loud. Outside it still has a nice sound.... Power wise it feels the EXACT same...