Useless to discuss changing anything until you say what you think the current deficiencies in the sound are and what you are wanting to hear that you do not currently.
I don't entirely agree with this statement. Sometimes, especially at the level of performance of the bulk of the gear the OP is using, you aren't aware of potential upgrades in SQ until you actually hear the difference it can make to swap out components for better ones (or ones with better synergy to the ones you have). I would also hazard to guess many folks here just upgrade to strive for something even better than they have, without even having a particular complaint about it. That said, certainly, if there is a specific complaint, it would help others speculate on what to change, and on that level I do agree with the statement.
Other than that, I'd agree with others who've pointed the finger to the front end components. Transports can make a difference. Going to well-implemented PC audio can open up a world of listening potential to you. Since I went to a computer storage library and software interface I listen to a greater variety of music and listen more often. So I'd also agree with MapMan's recommendation of ripping your library via a good ripping software (NOT iTunes) in a lossless format (AIFF, ALAC, FLAC) to your PC, and use an interface like the SB Touch (use an Ethernet cable to your computer for the best results) to a good DAC via SPDIF (I'm not familiar with your DAC to make any comment there - but DACs have come a long way in the past 10 years). This has the potential to sound as good as, or better than spinning physical discs on your transport. You will probably wonder why you didn't do this long ago.
The other huge potential for opening up another world is adding a vinyl front end, but that's a whole other ball of wax, and you may not want to deal with all the related expenses and hassles of vinyl playback. You also may simply not hear it as an improvement over digital for a number of reasons. I personally do hear it as superior in some ways, but don't want the hassle (proper setup and tweaking of rig, constant cleaning and care of LP's and stylus, much more delicate handling of all aspects of playback and related degree of patience which I don't have, storage of LP's). Though LP's sound better to me, it's not to a large enough degree that I'm willing to put up with the detractors, but you might feel different as many others do. If so, that can definitely offer some degree of improvement as well as offering up a library of inexpensive (assuming you enjoy garage sales and thrift shopping) and sometimes otherwise unavailable music.