I found this page which is quite interesting and it has many pictures of the early Marshall gear used by the Who that I've never seen before such as the 8X12 cabinets and other early 4X12's.

The side and rear view of the 8X12 is interesting because it shows how it was a combination of open back and closed back designs in a single cabinet, check it out.

http://www.thewho.net/whotabs/marshallstack.htm

In a roundabout way was responsible was the greatest amplifier of all time ?

You know in "join together" when he starts to break out in the solo it sounds so fuckin good ! and then just POOF ! it's over as soon as it started . major woodkill , nevertheless it's my favorite town solo atually it's the ONLY SOLO OF HIS I CAN THINK OF .

It is somewhat odd but then if you think about it Pete's guitar style was very much about using the power of the electric guitar so having a large great sounding and powerful amp behind him was what was needed.

I found it to be interesting how the Marshall amps were developed gradually over time. I guess because Marshall was a small outfit these changes rapidly made it into the production equipment and this is probably why the '60's Marshall's seemed to vary so much. It's not just the tolerance of the parts but the results of gradual changes as the results of this tinkering.

One of my dear departed friends had a "Vintage" guitar shop long before it was the domain of doctors and lawyers. I once played a Plexi 50 through one of the old 8 x 12 cabinets that he had in his shop. It sounded great, but how could I haul it around? I think it was quite a bit larger than my cousin's SVT cabinet. I really wanted the red plexi half stack however...