might be that the unit is producing a cleaner sound than you are used to
I used to run a lower line Kenwood and when I switched to the dnx8120 I didnt like it at first
took me a while to really appreciate it .
It IS more of a cleaner signal, I think you might be used to the bass boost and loud functions being on, im not saying thats a bad thing, some people like it. If thats the way you like your music to sound cool.
What kinda music do you listen to?
Try some Eric Clapton on a CD, not a burned cd but a store bought.
Thats the kinda details the 505 is known for