Best DAC for around $10K new or used

My top 4 were

ARC
Aesthetix Pandora
DCS
MSB Analog w premium power supply.

i set range at up to fifteen K new. Agree there is no such thing as BEST...

They all have virtues and leanings but in end I went with Pandora. have since upgraded it to SIG and there is another level of upgrade possible w stealth caps.

i think Jim White is a really talented digital and analog engineer, wanted a path to upgrade vs replace, appreciate tube rolling and also with path to DSD which the SIG has. Some future proofing provided by FPGA approach ( other dacs but not all have this) and finally an engineers engineer approach to Farady cage and some control of RFI and grunge.

My 2 nd choice and it was close is the MSB Analog.

I would say that the home audition is perhaps MOST important step.

No and yes.
Relied on my dealer and a few others I trust who believe that a preamp of good quality yields better sound. I am not seeking to add fuel to that debate. i believe the volume control and buffering in my ARC 5 SE would qualify as good.
They also did not stock or demo the feature. dealers I screened all four DACs prior to home trials were: Sunnys ARC, Audio Alternative Aesthetix, ARC, Nuts about Hi Fi Aesthetix. borrowed a MSB from a bud. DSC and ARC at Optimal enchantment. The VC is a relatively inexpensive option on the Pandora at $1K. But again nobody seemed high on it. Some downright against it.
Tube rolling yes. i spoke w Glen at Aesthetix and he recommended Andy at Antique Tube Services. rolled in some small motorola RCA and Bugle Boys.
I also have some cryo treated Russian Rockets that are very nice.