Hi jadedavid,
Does your Frankenstein MK II have 4 and 8 ohm speaker taps? If so which are you using? My Frankenstein MK II is an earlier model which had 8 and 16 ohm taps. As Mac wrote they were exceptionally good with his DIs using the amplifier 8 ohm tap.
If you do have a 4 ohm tap how does it compare to the 8 ohm tap?
Lak,
I can't imagine that you would have any issues at all using your Allnic 300b SET with the Double Impacts. In fact I strongly suspect that this pairing will sing as this is an easy speaker load. This has been confirmed numerous times on this lengthy thread. Your Allnic SET isa very high quality amplifier.
Charles