Krell KSA100 vs Threshold 400A vs McCormack DNA 0.5

The problem you are describing is an issue we now see frequently on the original DNA-1 and DNA-0.5 amplifiers that are now over 25 years old.

It is an issue that we no longer consider repairable. The problem is with the through-hole plating between the top and bottom of these two sided driver boards.

Repairing failed components and mending the connective traces can sometimes revive the amp for a short time but doing this is not recommended. The underlying problem is still there and it will continue to get worse.

Why would Steve offer upgrades to amps that will probably fail in the near future?

Steve is not doing that.  When I called Steve about updating the 18 year old mod. on my DNA-1 Deluxe, the first thing he told me was that if I sent it in they would have to replace the Driver Board as that is the part of the amplifier experiencing failure issues.  He offered to do more than that but said he could not repair the old driver board for reliability reasons, but that the board would be replaced by a new upgraded board.

Once the new board is in place you are good to go.  I went ahead and had the "Gold Special" upgrade done.  It sounds great and I have every expectation it will outlive me.

Some peoples mentionned that GAS Son of Ampzilla is a great amplifier.  As my DNA 0.5 will be repaired this fall or winter, someone offered me an ultra clean GAS Son of Ampzilla recapped. As I need an amp soon I'm tempted if it is really an amp alone in it's class. At least,(not like the DNA 0.5)  it can be easily repaired or upgraded by DIY. Seller wants $460 USD ($600 CAN) for it. Any comments ?Thanks

Good to know HiFi.
Is McCormack still in business with Conrad Johnson?
Apparently not. http://www.mccormackaudio.com/index1.html

@legarem: That Son of Ampzilla for $460 is an excellent choice! I own two of them! And I bought one brand new in 1977 - and stupidly sold it! Still a contender for "best sound per dollar"!