I love these cabs and they seem to be made for the Einstein biut I never hear of anyone using them together. I have a bunch of gear to get rid of and the Einstein may be in my future.
I use a Diezel Einstein combo with a Celestion V-30.
It sounds great.
I also try it sometimes with a Diezel 2x12 with G12-H-30's in combination with the combo and it sounds great as well. The definition and articulation of the tone is stellar! It is not needed to be played loud to get the fuller tones, either.
I run my Einstein with 2 Marshall 4-12 cabs. One with V-30s and the other with G12H-30s. Outstanding! is all I have to say! I would say go for that 2-12 that C-4 is talking about. 2 speakers is much better than 1.
This is the Diezel 2x12 with G-12-H-30's that Peter had built for me.
I have a Marshall 1912 with a 150 Celestion in it that also sounds good as a 1x12 extension cab with the Einstein combo, but it doesn't sound as good as a Diezel cab.