Your system looks pretty darn good already. What will change the way your system sounds the most would be changing speakers - not even talking better or worse, but that a change of speakers and placement within the room will make the most significant change by far. Now if you love your speakers and are asking how to make the system better centered around your current speakers, that would be a different question - and I would probably start with the amp that really matches well with your speaker of choice. And your analog source would also make worthwhile improvement - some will argue between the importance of source versus amp/speaker, but they are all important. But like said, if you want to change the basic sound you are getting, speakers first IMHO.
