I heard all of those heads, and was fairly impressed. The TH500 sounds just like the Tonehammer pedal - go figure! The AGS isn't as aggressive as the Aggro, but can add a little hair. The Streamliner 900 was very warm/round/vintage, and quite nice. The ShuttleMAX 9.2 is super flexible, and can do just about any tone you'd like.
That being said, what really blew us all away was the GK MB800. It packs a very visceral punch, and is the first micro head I have played that you really feel in your gut. Sure, gain matching is king; this was NAMM (which is a terrible place to actually hear things); we didn't do a direct A/B/C, etc., but based upon first impressions, at least, the MB800 really impressed. In fact, we gave GK one of our Best of Show Awards for the MB800.
Tom.
I bet that GK is just a hammer, given how loud the MB500 is already. Not really my thing tonally, but I imagine that head would be the 'volume king' among micro's. I assume it is a ways out from going into production and distribution.

