my advice is: change the receiver only if it does not have enough power or it's missing on some features you want.
an unnecessary change will not improve the audio quality.
what would change the sound quality would be for you to get a new sub that will go down to 16 Hz; it is good for music sometimes, but much more so for movies.
there is a world of difference between a sub that goes down to 25-32 Hz and another one that does well right down to 16 Hz.
THAT would make a big difference for your listening pleasure.
