I bought a HarpGear Double Trouble this weekend. Wow. It was amazing. I will write a large review soon. I had a DT a couple of years ago and don't remember it kicking that much tail. I did a full five-piece gig with the amp on 4...I could turn up to 8 without feedback. It is easily three times louder than either of my Champs. In fact, I sold the SF Champ and have the Vibro Champ for sale as well.
I did the gig with the stock speakers and tubes, but have already subbed in some JJ 6V6 tubes and a GE 12ay7. I plan on testing some Weber ceramics in the amp too. The AlNiCo speakers are fine, but with the amp cranked and a low F harp, there was too much speaker distortion for my liking. However, a lot of harp players enjoy that sort of breakup. My preference has always been for ceramic. I think the bottom end is tighter and the sound of the amp has a better spread. AlNiCo has always seemed beamier to me.
But I am not an expert!