Best option for Amp upgrade...

With amplifiers, new is not always better, particularly when comparing to Class D.  I would be curious about how many of the folks saying "sell" have owned McCormack gear, and particularly how many have owned his amplifiers with full SMc upgrades. 

I have a DNA-2 LAE  with SMc Signature upgrades and it sounds great.  I chose to keep that amplifier over a pair of Ncore, NC1200 monos.  I also own a pair of high-powered conventional Class A monoblocks that are in my main system.  I like the Class A amps better than the McCormack/SMc amp but both sound good. I believe there is a picture of the DNA-2 on my system page and the work quality is exceptional.   You would be hard-pressed to find that quality in an amplifier today under for $10K or even much more.  BTW, more than most other manufacturers, Steve has a history on his gear and he is very aware of which parts are at risk of degrading or wearing out and he will address any of those issues during the upgrade.  If you like the sound of the amp now, the upgrades will improve on that.  The sound will still be similar (i.e., it will not be a totally different sounding amp) but it will be more refined,  with improvements in tone, treble smoothness, and maybe dimensionality, among others.  BTW, I have also owned the DNA-500 and it is a very nice amplifier.

Those who mentioned the resale value of an upgraded amp being less than a similarly priced new amp are correct.  Therefore, you need to decide if you plan to keep and listen to the amp because you like how it sounds, or if you are more likely to get on the buy/sell merry-go-round.  If you like the amp, and just want to make it even better, then the SMc upgrades are a great value.  If your goal is a better resale margin, then the upgrades are not for you. 

I wouldn't worry about the age of that amp....it is a very good design and built like a rock.  It will be dead nuts quiet and totally reliable when Steve is done with it.  As I recall from owning the DNA-500, and using it with a wide variety of tubed preamps and mostly with a Tom Evans Vibe/Pulse SS preamp, the amp displayed very good clarity, dynamic, hard-hitting bass, and good dimensionality.  The weak point was a small bit of wispiness in the treble, which Steve says is corrected as part of the upgrades.  I do not remember resolution and detail being issues with that amp.  Maybe you need to try a SS preamp like the Tom Evans or better yet, Steve's own TLC-1 with Signature upgrades, which is the best preamp I have owned out of about 20, including several that were north of $10K.