I've played and played with my Archon. I have not tried every speaker, or even every one that I really want to try. I'd still like to try several of the Warehouse V30 type speakers, and the ET90. I've love to try their version of the EVM. I've always wanted to try Scumbacks. Still haven't bought any.
But I have concluded lately that my favorite speaker with the Archon that I have tried so far, is the Eminience EM12 in the Mesa Thiele cab. Each speaker and cab I have adds it's own character to the tones. While I know that the Eminence and the other EVM type speakers are not "flat," so they do contribute to the tone by some frequency variances, the cone itself does not contribute as much "character" to the tone. You hear more of the amp.
I remember doing my speaker tests with the Mesa stuff and found I could get rid of the ice pick some people complain about with Mark amps, by using higher power greenback type speakers. It also sounded more Marshall-like when using them. I've said this before, but I wish I'd had the Emi speaker when I had the Mark V and Mark V25. I had the Thiele cab but with the stock C90 speaker.
I like the Thiele/EM12 combo so well, I decided to buy another Thiele cab. And then Mesa raised the price of them $100, which raised the price on used ones. I bought the Dr. Z Zbest cab, which is basically a 2x12 Mesa Thiele cab. I'd drop 2 EM12s in that thing in a heartbeat, because it's a great sounding cab as is. But, it is the older version of the cab. 2 years ago the good doc decided they were great but lots of people weren't buying them only because they were too heavy. So he switched to pine, dropped 19lbs off the cab weight on the new models. Mine is about a year before the switch. That thing with two EM12s would weigh more than most 4x12s! LOL I still might do it some day. But I'm afraid it would knock down a wall in my home. So for now, Archon and MT15 owners, I'd suggest finding an aftermarket Thiele cab and dropping an EM12 in it. While heavy for a 1x12, it would easily replace most 2x12 cabs more than adequately, and the EM12 is just killer with the Archon. I even thought about putting one in my pine PRS cab... but think about it. Handle is on the top/middle. One side would weight 10lbs more than the other. It would be totally out of balance, if you were moving it around.