Really, for most practical purposes the only difference between 70V systems and home audio is the math. The 70V math used for commercial applications is more straight forward. In many respects one could use "25V math" for home audio -- but you'll still max out at two pairs of 8-Ohm speakers for most amplifiers. Of course, you could resort to autotransformer volume controls for the home system too. (Ever wonder why these home controls look exactly like the 70V controls, but with home friendly trim plates?)

And, the traditional 70V volume controls are ugly -- and not usually available in stereo. (but, dig around, friendlier controls are out there)