Upgrade McCormack or...

I would definitely go with SMcAudio's upgrades.
Pat and Steve provide excellent service, and you can spend whatever you are comfortable spending- though their standard upgrades are probably the way to go.
The nice thing is that they will tailor the upgrade with the equipment you are using.
Though I would ask them for a time frame, if you need the amps upgraded quickly. Sometimes they get a backlog that can keep things from getting upgraded quickly.
BTW, they upgraded my DNA-1's to monoblocks as well as upgrading my Micro Power amps to monoblocks and Micro Line Drive.
All of which perform way beyond their original configuration.

Bob

@cheeg  I've had my DNA-1 Deluxe for 22 years.  I had it upgraded by SMc Audio 20 years ago and after realizing it had been that long, I contacted Steve to see what he might do to upgrade and update it.  As it turns out, he explained that over the last few years he has had some well-healed clients ask him to build them ne plus ultra amps.  In the process of meeting their desires he discovered new ways to improve the DNA line.  Suffice it to say that I sent my amp. to him and just about every component of the amp save the transformer and Nichicon Goldtune output capacitors was upgraded.  The amp I received back was entitled, "Gold Special".  The McCormack name badge was replaced with an SMc badge. 

If the originally modded amp was a diamond, the Gold Special is a finely polished diamond of nearly perfect color and no occlusions.  It passes every bit of the musical source with no added distortion.  The openness and clarity, the bass attack and woody resonance of a string bass are all there.  I will never part with this amplifier!
Steve, Patrick and the rest of the SMc crew execute their work with care and precision.  If you allow them the opportunity to work on your's you will not be disappointed.

I've owned about a dozen McCormack products over the last 25 years, both stock and modded. In agreeance with rsf507 you do want to keep them to get your money's worth, but high end audio is not an investment, you almost always lose $ down the road. Selling the DNA-1 and buying another amp may or not reach your "audio nirvana" then you'll probably lose twice. I can say with proven experience, having owned a stock DNA-1 and a gold upgrade at the same time, there was a huge difference in sound quality, clarity, soundstage, etc. SMc upgraded equipment does resell quite well as I have experience on multiple occasions. 

A couple years ago I sent my pair of DNA-225 amps to SMc to have converted to mono amps and have them upgraded along with my LD-2 preamp to silver status. It was during the holidays so it did take a few weeks longer but Patrick will call and/or email you as much as you like to give you play by play updates and recommendations. When completed, Steve with audition them for his final approval and he may call you himself or he may answer the phone when you call. Upon receiving the equipment back I can testify that both the $ and effort were well spent. Without even burn in time, these amps could hold their own against Pass, Rowland or Levinson, all whom I've had experience with. 

One more note, in my last conversation with Patrick I believe he told me that they now had the ability to upgrade and work on their faceplates, either etching or laser to redo the often problematic silk screen lettering on some of their older products, or maybe to just fancy them up a little. We all know that the DNA's never won any beauty pageants, but then neither did Mike Tyson.

over the last few years he has had some well-healed clients ask him to build them ne plus ultra amps. In the process of meeting their desires he discovered new ways to improve the DNA line.

@hifiman5  and @joecollege  are correct, the SMc upgrades have significantly improved over the years due to Steve's work for clients seeking the best possible amplifier he can build.  I wouldn't be surprised to see him develop and bring to market a new amplifier independent of the McCormack upgrades, as with his VRE-1C preamplifier.

Currently, about the only things they reuse from the DNA amplifiers when performing upgrades (assuming the client chooses the higher/highest level of upgrades) are the chassis, heat sinks, and transistors. They can reuse the transformers but prefer to replace them with Plitron low-noise transformers.  They actually don't care whether you send them non-working DNA amplifiers since they can replace everything except the heat sinks and chassis.

The project they are currently working on for me will indeed include new custom engraved faceplates that will match the faceplate on my SMc preamp.  They offer a variety of colors and engraving options, to meet the desires of their clients.