I STRONGLY recommend ISIS, but ONLY if you are planning something more than the usual suspects when it comes to accessories inside your car. If you are planning the typical electrical components then ISIS is a waste of your money, but if you are planning to expand greatly and want to get into the world of modern electronics in your build, ISIS is the way to go. I'm still debating coupling mine to MiMod HP which would expand even further on an already awesome system AND allow me to control my air suspension from the touch screen display while eliminating the only somewhat aesthetically pleasing control panel from Ride Tech. But that doesn't answer your question.
Ironworks Speed & Kustom is now building and selling "Hot Rod Fab Parts" that he is marketing to the home builder, to simplify certain aspects of the build. One of those parts are mounts for the ISIS Mastercell, Powercell, and InMotion controller. They sell for $20 a piece + $15 shipping for as many can be put into a USPS flat rate box. He put 5 in mine with a lot of room to spare. I could easily have fabb'd something to mount the cells but I like what he has and I'm planning to do something cool (I think) with mounting all these electronics. These are just a real simple piece that save a lot of time.