I really can't see a 2 watt tube amp hurting your k110 JBL's, but they are probably not the best match for it either because of their high wattage. On a daily basis we put a small amount of wattage through our speakers in our practice amps, and they seem to last just fine. I mean, who really cranks their amp to 10 everyday at full wattage? I would try using just one with the microbaby if I was at the helm, thats all you really need for that application anyway. Your going to be using an SMS preamp with a hotter signal than the microbaby's pre also, but I dunno what that extra signal translates to in wattage out of the power side. I assume its a bit louder (or could easily be) when you hook the SMS up to the microbaby? My old Mosvalve combo amp manual said the wattage was 100 watts but with both (pre) tube drivers stacked it could be significantly more than 100 watts that it could possibly blow the speaker. Again, I am not an amp expert, that could be the square wave (distortion) causing that issue. I really don't have an absolute answer on how all that equates between pre signal and power side signal.
With your rocktron, I would be very careful at loud volumes, but I wouldn't be afraid of using the cab with it. 150watts could blow those original cone vintage speakers if it gets away from you, but that would be at a high volume. At lower volumes I wouldnt be scared to play through both of them at say 1/2 volume clean (be sure not to unplug your guitar with the amp real hot).
I have seen 40 watt tube amps a 25 watt speaker in them so, you just have to be careful on the higher wattage amp to lower wattage speaker. But, that rocktron set up is probably more suited for that 2x10 cab then the microbaby, so you could use them for both really!
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