This is the Steel panther Butthole Burner into a Fender Vibroverb:
The Okko Diablo is really good, too. It sounds darn close to my JCM800 into the low input of the JCM800, or a Fender, or the clean channel of the EVH 50S or Mesa .50 Cal+.
A DS1 into a cranked Fender is the Nirvana dirt sound. My Analogman DS-1 nails that sound.
A Deluxe Reverb or Bassman on the edge of breakup, pushed with a good overdrive or distortion can get Marshally in a great way.
Loud volume is the key. Push some air. Get the power tubes breathing. My bf Dual Showman has to be pretty loud to sound good with dirt pedals.
But a good Marshall has to move some air, too.