I'm sorta on the lookout for a counterpart to my GB Streamliner 900. I was thinking the GK might be it. I been doing alot of amp research here past few days too.
I run the 900 thru a 4 ohm, TB153 so that cab prolly would get the most use. I also have 2x Neox 212T's, 2x UL410's (8 ohms each) and 2x TC-RS210's that I primarily use at my gigs with a few different bands. And I own GB Neopak, LMII, F1 and Carvin B1500

; the B1500 gets very little use if at all.
So I'm wondering what higher wattage mini-micro head might work well when I don't need what the GB 900 does. Hey maybe the GB 9.0, don't really need all the 9.2 features. I'm also researching the Aggie AG500SC, as many threads say this is a clean sounding amp.
From the few U-tube vids I've seen, the Aggie sure does not seem like it would serve a different purpose than the GB 900. Maybe its the way those folks set the Aggie, no chance to play one first. Sorry if I've coat-tailed on your thread. Maybe some folks can speak to what the MB800 does different than other "tubey" amps. Peace, ernie.