Well, I've got a Line 6 Flextone II HD. I used the cab's new setup last night at band practice and there was a hugeeeeeeeeeeeeeeeeeeeeeeeeeee difference. My other guitarist was a little confused at how my amp was so much louder than his. I'd say that the volume increase is at least double, and the tone improvement is leaps and bounds beyond what I expected. As soon as I can afford it, I plan on going with a quality tube amp.
But for now, I'm running the Rocket 50s in that cab at 8 ohms. I'm working on a cab that's going to house two of the 16 ohm speakers I took out. Wired in parallel, that would give me an 8 ohm load. And then daisy chaining these cabs, I would have a 4 ohm load, right?