Right now I think my setup sounds pretty good.
My advice - if it ain't broke don't fix it chief. Spend the money on music.
I think the obvious hole in your current system is bass. I'd add a subwoofer.
Subjectively, it's "to each their own" as to which DAC is preferred. Objectively, both the DAC1 and the DACMagic were measured in Stereophile. You didn't say what your source component is. If you're using the USB input on the DACMagic, then without question the DAC1 USB is better.
Most of the dacs will be a sideways change at best. The idea about a sub is an excellent one. Don't know your listening room so I cannot recommend size. I just went through a sub purchase exercise and picked the Paradigm sub 12 after listening to the Rel B series and the JL. I wouldn't even consider the B and W sub.
OK, I've listened to the Benchmark and the DACMagic in very good systems but not the same systems and not head-to-head. Still, I did not hear, from either unit, the kind of highs that I would want to live with for a long time.
DACs I have heard which did give me the smooth, clear highs I can enjoy include the Ensemble Dichrono HiDAC, the Audiomat Maestro, the Stellavox ST-2 and the Apogee Mini-DAC. Of these, the Apogee is the cheapest.