I've owned plenty of McCormack products (several of his preamps and still have two modded amps). I've had multiple rounds of mods over the years, so I'm intimately aware of the performance from stock to various levels of mods in history up to as recent as 2 months ago (the last time I got an amp modded with the latest and greatest including some things he did for the first time on my model). I also own ARC, McIntosh, Emotiva, digital amps, and many others over the years.
In terms of which one of the three above to buy, it's pretty much a no brainer. In stock form, they are all long in the tooth and not going to be super reliable nor up-to-date. If you don't want a tube amp, an old Class A isn't going to be much better in terms of heat issues. Plus, it's going to be less reliable. The board is probably warping with all the heat/cooling over the years among other issues that I wouldn't want to deal with.
The only one you can get upgraded to be 100% reliable and warrantied is the McCormack. Plus, it's the only one you can get modded to state-of-the-art modern day performance customized for your speakers. Part of the modifications that Steve does is tailor the voicing to your other equipment/listening tastes/etc. You will never have to buy another amp again because you can always send it back for new mods like I have for like 20 years now. It's night and day from stock form and my amp now makes the internals of the $55k Dagostinos look like a toy for a fraction of the cost.
One thing that people also don't realize is that you can modify the "looks" too. I've never personally invested in modding the looks, but my friend has Ayon tube monoblocks that look great, so he wanted his modded McCormack to be aesthetically in a similar league. As a result, they are doing some custom work on that end too.
In legacy stock form, I would agree/disagree with what's been said above. It's probably not the amp for those that like "tube" sound. . However, it's not because of it's interface with speakers. It's more about the source feeding it. (BTW, in full-monty modded form, it's better than my ARC Reference amps)
In stock form, it was built to a modest budget level and delivered a surprisingly high ceiling performance, but building an amp to a modest budget is also a kiss of death. Many people will mate a modest budget amp with a modest budget source that may not have the same performance ceiling. (MFGs have figured this out and that's why prices are so ridiculous nowadays. They stick a high price tag on their products, so you and reviewers will mate it with theoretically other high price/high performance gear and not feed it junk.) Modest gear that performs on the same level as high priced gear often gets shafted and false reputations because it gets paired with lesser quality sources. Krell and Threshold were far more expensive back in the day, so much of their reputation compared to McCormack is based on being also paired with higher level of sources in most people's systems.
Just to be clear though with my recommendation. It's a "no-brainer" assuming you are getting it modded. As good as it was in stock form, the McCormack is past it's useful life and all the driver boards need to be replaced at this stage of it's life cycle. If you are looking at those 3 options for use in used stock form, I say the "no brainer" answer is to buy NONE of them. Get a much more current used amp or something new from quality budget suppliers like Emotiva, Parasound, etc.
Good luck.
