Should I eliminate my preamp?

This is exactly what I recently did. I bought an Oppo Sonica DAC and asked myself "what do I need a preamp for?" Like you, I have an ARC pre-amp (SP-6B) but since I no longer listing to vinyl, I was just using it as a volume control. The Sonica DAC has a perfectly good digital volume control which sounds fine to me. Plus, the Sonica DAC has balanced XLR outputs, and my Rane AC22B crossover has balanced inputs. I noticed a marked improvement in quiet when getting rid of the SP6B and it's single-ended interconnects, and moving the the DAC/Crossover/balanced XLR setup. How could an extra piece of gear in the signal path improve anything?

My SP-6B recently came back from service at ARC, and I'm am wondering if I should sell it. There are a lot of new vinyl fans out there who might want it (along with my SOTA Sapphire turntable, Linn ITOK II tonearm, and the Dynavector Karat 23R cartridge).

This discussion reminds me of the time Bob Carver made his non-audiophile solid-state amplifier sound exactly like a Stereophile Class A Conrad Johnson tube amp by adding distortion. 

Fake news

Real news. Google ‘Carver Stereophile Challange’

The theory is correct. Any preamp will add frequency response anomalies and distortion. You may prefer that sound to the unmodified signal, but it is good to be honest (as most of the posters in this thread have been) about what is actually going on. Sometimes I enjoy the listening to different DSP settings in my Yamaha A/V receiver  :-)

The OP was asking about getting rid of the preamp in the case when the DAC has a volume control. In that case, there is no downstream volume control, and no need to provide a low impedance buffer for the interconnect, as the amplifier will take care of that.

Yes, but the OP asked about using a DAC with volume control as a low impedance source to drive the interconnect to the amplifier. There is no passive attenuator in this scenario, and from an engineering standpoint no need for the preamp. The people arguing for retaining a preamp are arguing that they prefer the sound of the preamp. That may well be, but it is not more electrically accurate. The preamp is providing a subtle distortion that sounds pleasing to them.