I will say that compared to the Dialogue One, it is a step up for sure. It has much more clarity, and better sound stage. It has the power handling I was hoping for and seems to have a smoother overall sound. I like it, and will definitely be keeping it. I opted to put KT120s in it after only a short time with the standard EL34s, and I think this was a good move for the kind of music I listen to... mostly classic rock.
But, the real question is whether it's the major step forward you'd hope, based on its cost. I would say it is a step forward, but probably not the major leap you'd expect. If I was to go back, I'd opt for the Dialogue Premium instead and spend the extra $1k on music. I don't think the extra power makes a substantial difference. Even the Dialogue One handled my B&W speakers quite well.
At some point in a year or two, I'll probably put the KT150s in. But, I'm very happy with it at this point and don't feel a real need to upgrade to the higher power tubes. Perhaps the KT150s would have a touch more power behind them, and may sound a little sweeter than the 120s. It would be a fun experiment, but spendy.
If you are facing this decision too, and the cost is a stretch, I think you'd be just as happy with the Dialogue Premium as with the HP. Frankly, even the Dialogue One or Two are awesome as well, and I think anyone would be happy with any of the PL integrated amps. If you are in Minneapolis, bring a beverage of your choice, and I'd be happy to give you a demo!