I use an A21. Happy with sound. And, delighted with recent improvements to sound resulting from replacement of stock fuses with HiFi Tuning Supreme units. Speed and resolution has improved, and sound has more presence. Remarkable improvement for a modest investment. See description of change and account of experimenting with Furutech TF Audiophile fuses in my recent post to following thread:
My system: Bluesound Vault 2 --> Parasound Halo JC2BP --> A21 --> Vandersteen Quatro Wood CT.
Curious to hear your impression of comparison between A21 and JC1.