I traded a JCM900 head for one of these, and like you, found it doesn't matter what tubes you use, it sounds like crap. Plus the clean channel is so anemic you can't use it if you're playing with others. Although the Marshall was too much for what I was doing, I'd trade back in a second.THD univalve. Noisy, cold, hard, lifeless, sterile. Didn’t matter what tubes I used it always sounded and felt like ****. The guy I sold it to wasn’t too impressed either. He contacted THD because he thought I sold him a broken amp. They said “no, seems to be acting fine”.
I did regret buying my Egnater tweaker when the first transformer died in a month, and then the second fried after I left the amp on overnight. Now it's got a Mercury Magnetics tranny in it and we're having a cautious reconciliation.