I just picked up a Rockwell grinder myself, I'm glad other people have them too, I couldn't find much out about them!
Mine is much louder than the 4x36 it replaced as well.
For a quick belt purchase I went to Lee Valley, but supergrit is around half price on most belts (although I did find that the 15 micron belt was only 50¢ cheaper! But I am also Canadian, so that accounts for some of the Lee Valley difference.
Hope you like your new grinder! Mine is taking me a bit of time, but I have only worked on a couple of blades this far, and am used to the radius available on the 4x36, but love how much quicker the new grinder hogs off steel- a real grinder must b incredible to use!