I have a Marshall Valvestate 8040 from 1995. Is it possible to use it as a speaker for Garageband, connecting this amp to my Focusrite Scarlett Solo?

I recently purchased a Focusrite Solo to allow recording on my computer from the DSL40CR. 

The output from the emulated output is just awful.  Sounds muddy, like a blanket is over the speaker, etc.

Doing some googling leads me to believe this is normal for the emulated output.  I just don't understand how Marshall can makes products with features that flat out don't work.

Has anyone else had any luck with the emulated output?