Is my DAC my weakest link?

I recommend the Chord Mojo. There is one currently listed for less than $400 on Agon. It's not mine. I use the Mojo as a headphone DAC when traveling. I know that others on this site use the Mojo as the primary DAC in their home systems.   

+1 @erik_squires on the Furman recommendation for your system. A power conditioner basically does what it sounds like it does. It makes sure the power your system sees is, in easy terms, "clean and steady." The electricity coming into your house has audible noise in it and it doesn't always (or ever) come through the lines in a uniform, steady flow--electricity surges--and a power conditioner helps harness this attribute and provide your equipment with a steady diet of cleaner and steadier power. I've oversimplified but hopefully the explanation helps you. BTW there are many folks on this site who don't use any power conditioning because they do not think it adds significant value. I have run previous systems without power conditioning. However, I am now a strong proponent of using power conditioning. FWIW the Chord Mojo will probably provide you a more discernible audible improvement in your sound than an entry level Furman. But that doesn't mean the Furman isn't a good idea for you.