I have the Powerhouse 2700 and I love it (I also have the GREAT Champion these good folks are bashing). I have been so pleasantly surprised at the performance of this unit that I am considering buying a second one and the parallel kit--even though I don't really need that much power!
I have found that the Powerhouse 2700 performs as advertised all the way up to the stated 2600 max streaming watts. The sound is a low throatty rumble, probably close to the SPL of a Honda, but nobody is going to give you credit for having a Honda.
I've read positive online reviews of the parallel kit, but I haven't seen one in action. Can you keep us posted on your results? Good luck!