DAC Or Server - What to upgrade first?

I'm wondering what will give me the biggest upgrade in sound, a new music server (Aurender N10 or W20) or a new DAC (PS Aaudio Direct, Simaudio 780D, Berkeley Refence DAC, etc). I currently use a Meridian Sooloos MS600/MD600 server/storage system and a Berkeley Alpha DAC 2. Any experiences on where the best place to invest in an upgrade would be?

Rest of the system is Simaudio P8/W8 amplification and Revel Studio 2 speakers.