I had the original E670. Awesome amp, probably my favorite head, I had no problems getting it to cut in a mix. One guitarist band so never ran it up against another amp. E570 + VHT 2/90/2 stomped it though. And can confirm Pball Mk1 was a total turd, possibly my most uderwhelming purchase ever, yet the Synergy Pball rules. Never tried the Mk2.