The MiniMAX and more - the MOSFET-MAX - would be better for low-efficiency planars and small speakers. For all else, the Torpedoes (either one) are superior. The most noticeable thing with both Torpedoes is the greater transparency of the output transformers compared to output coupling capacitors. Output coupling capacitors, while pretty good with better quality audio-electrolytics, still puts a bit of a fog over the output of an amp by comparison.
As for the Torpedo III, it probably has another 10-20% improvement in detail, imaging, etc., over the Torpedo I. That said, you probably won't notice the most important characteristic of the Torpedo III until you switch to another amp or put in some long-term listening. The ECP Audio DSHA component of the Torpedo III means outstandingly clear and fatigue-free listening. It's difficult to describe until you've listened to one for awhile. It has an uncanny ability to render even the harshest recordings into something detailed and musical. The word "tizzy" is completely alien to the Torpedo III. At the same time, the highs are even more extended and detailed than the Torpedo I.
I don't know any better way to describe it, but maybe when we get these going, some of you wordsmiths can come up with better descriptions.
BTW, PCB's should be on order soon. I hope to get a quote for the production run tomorrow.