DAC or pream

I am currently running an A-21 Parasound amp to Magnepan. 7's. I stream exclusively now with Amazon. I am currently using an Emotiva PT-100 for my DAC and remote. I looked at a P6 but dont need the phone or other preamp features. 

Will I improve dramatically if I switch and what would you reccomend? I need remote volume control and USB input.