New dac

You have a very nice and well balanced system. The weak link on the PS DL 3 is the USB input. I assume you are using the DAC in the Node 2 for streaming purposes and the DL3 with your CD player as transport. I sold my first DL3 about 5 years ago, because I needed additional inputs (used a USB/SPDIF converter which took up the only coax input) converter. Just recently bought another DL3 to use in a second system. I believe the DL3 to be a very good sounding and well built DAC at current used prices. In my opinion it would take considerably more money to do much better (unless USB is required). If I was looking to upgrade beyond the DL3 I would consider a DAC that could serve both the bluesound and disc player. 

What is your budget for a DAC? 

Regarding the DAC question, I believe your DL3 mates well with your system. To better it would cost much more and may not return on that value unless you upgrade the rest of the system.  As I said earlier, the DL3's weak link is the USB input. At the time it was placed in the market USB was a convenience interface. If you want to use the USB input get a USB/SPDIF converter. I suggest a M2Tech Hiface, removes need for a USB cable, however you will occupy the coax input.