But you didn't like them in the Twin because they sounded thin. Supposedly due to impedance mismatch. Yeah, that sounds unlikely, so as was said, check your phasing. The other thought about that... perhaps because the Twin is a loud(er) amp, you turned it down more when testing, but didn't roll the bass up. General rule with BF/SF that as the volume goes up, bass goes down, and vice versa. Just a thought. That said, I've had speakers that I love in one SF amp, and hate in another. The JBL D120F pair (original cones) sounded flat in my Twin, but one of them in my SF DR sounded amazing. You could also try mix-n-match. One G12C, and one of something warmer, like a Celestion Vintage 30.