A21 vs McCormack?

Thanks for your responses — Bob, the rest of my system is:
Usher Mini Dancer 2’s
DNA-1 
Parasound 2100 preamp
Benchmark 1 DAC
Bluenote Vault
Cambridge CXU
Technics SL-D2 (rarely used)

I was planning to upgrade the DNA-1, but the recent cost drop of A-21’s, due to the release of the A-21+, made me wonder if that would be a more cost-effective choice for an amp of similar quality. I’m surprised no one has spoken up for the A-21’s, as they were John Curl design and I had heard they were very, very good. I’ve been very happy with my McCormack, and have heard SMC does a great job with the upgrade, but before spending $2K I wanted to be sure I wasn’t overlooking a great, lower cost alternative. 

Everyone -- thanks for your responses; it's a big help in deciding how to move forward.
@labtec: thanks for your detailed message and suggestions.  I'm having some trouble with my DNA-1 now, so I don't want to put this off any more; the issue was whether to send it to SMc, or go with another amp; given all the current options with Class D and other lower cost solutions, I thought I should explore it a little before going with the rebuild.  From all the responses, I think the rebuild is the right way to go.  However, I appreciate your advice on setting my other priorities; I have been fairly happy with the Benchmark 1, but I realize it's not SOTA.  How much do you think I should budget for an SOTA DAC that would complement the rest of my system, and would you recommend new or used?  As for the subwoofer suggestion, that is on my radar, although I'm planning to go for a swarm after I get the amp and DAC budgeted.  Thanks again!