Hey TB, I currently own the GK 1001RB-II. I like this amp but am in the mood for some change and switching to an amp with a tube preamp possibly. I have heard good things about the Mesa Big Block 750. But I have always wanted the GK2001RB-II. In addition to trying a new amp head I am looking to switch my rig from 4x10 and a 1x15 too 2- 2x12's. Hoping it will give me a tight punchy sound while keeping the low end. I also have heard of phasing issue from mismatching speakers. I'm not sure how much of this is effecting my sound but I think it would be tighter. I see a lot of posts with some company Fearful? I would most likely match the cab to the head but I am looking for some feedback from TB before I settle on that. I also see that GK is now selling amps with Tube Pre called the Fusion series. Have these been compared to the Mesa stuff? So what do you guys like?