Bro i think your facing the same problem as i. When i tested out the Sansamp gt2 over at tymc it sounded great enough distortion and chunk. However when i plugged it in my shitty peavey amp it sounded worlds apart. So i got my friend to check it out surprisingly it sounded way better on his roland jazz chorus. So man what i suggest check your amp theres no way to make a lousy amp sound good even with boutique pedals.
Hey man, I had a jam session with my band using a Marshall JCM and I still faced the problem. So, I don't think it's the amp in this case man.