Advice

Well a lot...but usually a price not commensurate with performance. What's your room like? Where are you speakers placed? Are you looking to spend money or keep this simple?

Calibration? (From The Princess Bride) "I don't think that means what you think it means." In any case, you seem to have chosen some nice components within that price range and you're probably not going to better them without spending a lot more. Look into some good power conditioning. I prefer Audience, but there are others. I know - Do I have to spend more on my conditioner than my DAC? Yes, if you don't want to screw things up.

http://www.needledoctor.com/Audience-adeptResponse-aR2p-Power-Conditioner

"I have a modest system and it sounds great. Looking for some calibration, i.e. how much better could it get?"

My advice would be to leave it alone. If you are really happy with your system, why fool around with it? You could just as easily make it sound worse than better.