How much difference in sound?

I am using PSB T65's for my speakers. If I can hear a better sound ,I would not be opposed to getting new (used ) speakers in the next year to put with a new (used ) amp if the sound would increase in quality. This is the route I would like to follow. I would like a really clear maybe nuetral to warm sound. I don't understand quite yet what this would cost,but that is where I want to end up without going through numerous units,speakers, etc. ,(if that is even possible)

Room is 12 by 16, and music is rock,classic rock, jazz, blues

Thanks for all the input,
I guess I have the upgrade bug, wanting a full brillant sound on the least amount of $'s needed to have that sound. I am willing to preceed piece by piece to reach that rainbow sound in the sky.
I believe that I will shy away from tubes, and look for SS amp and pre.
I am using an onkyo cdp that is about 14 yrs. old, would like to upgrade the cdp too.
I guess I should start with the amp,then pre, then speakers?
Gary

Any suggestions on a cdp that will be a nice piece in the system if I do choose to upgrade the amps in the future?
gary