What External DAC pairs best with Audio Research Equipment?

staying in house always gives some assurance of good matching of gear and tonality but beware that companies such as arc have been around for many many years and their gear from different decades can sound somewhat different and mate as differently as different makes of gear

second point is in my experience if you have a a fairly modern (2000 and forward) arc pre/line stage it will take the input of any modern dac just fine -- so go for what sonic flavor of dac you see fit to suit your personal musical palette

The DAC 9 is almost 10 years old and DACs have improved a lot since then. I also don't think DAC/linestage matching is particularly difficult, so my approach is/was to get the best DAC I felt would be the best fit for me in its own right, within my budget.

I have a Mola Mola Tambaqui feeding into an ARC Ref 10 linestage. It's a pretty fantastic combination.

I’ve A/b’ed myTopping d90III Sabre dac against the Hegel.   It compares very favorably and is more towards the detail goal stated with similar excellent soundstage so that might be worth a try and save some $$$s to boot. You can hear every detail in a recording including incredible micro detail with instruments in good quality recordings. 

given the generally understood excellent tonal, timbral  and imaging traits of top arc gear, i would think that modern clear, open, very liquid but fast sounding dacs such as the following would synergize well (these from personal ownership experience):

weiss

gustard r2r, for a lower cost option

better chords (qutest and up)

msb

bricasti m1

Thanks all!  great answers! I think I’m gonna give the Weiss 204 Mark 2 a shot I’ll let u know how it sounds when set up & lived with 😂