In Jersy I know for a fact that a licenced electrician nees to do your work.
That being said you can put in a 100 amp box but only pull 50 amps from it, but in the future when your house sells or you forget you end up overloading the feed with a big box. I am sure that would not pass code, but if you are doing it yourself and never tell anyone, go for it.
I pulled 60 amps out to my garage with copper standed. Used 4 seperate wires, two for power, one to tie back to the house ground, and 1 for a redundant gound.
In a house I assume all that wire will have to be in conduit to the extra panel as well.
1996 F-250 extended cab long box five speed. Home made Tymar, 203 Stat, 60 gal in bed fuel cell, 315/75's, no muffler, ebpv welded open 3" to 3" DP, Babies. 290K, still chugging, and still smoking when cold.
UPDATED 1/1/09 Replace so far. 1 LUK flywheel+clutch, 2 thermostats, 2 set of brakes, 1 set of calipers, 5 CPS, 3 sets of tires, 2 Transfer pumps, 1 Injector modual, 1 Computer, 2 Alt, 2 sets of batteries, 1 Water pump, 6 Belts, 1 PS hose, 2 Sets ball joints, 2 set u-joints, 2 carrier bearing, 2 Speed sensors, 1 oil pres sender, 1 temp sender, 4 sets of e-break cables, 1 front fuel tank, 2 rear fuel tanks, 2 set of glow plugs, 7 Glow plug relays, Oil galley o-rings, Turbo pedistal o-rings, EBPV o-rings, 3 sets of Injector O-rings, 1 Vac-pump, 1 new carpet, 1 total paint job.Total $$$ in repairs v/s miles driven = 4.6 cents per mile. Add fuel to that it jumps to 16.5 cents per mile over the life of the truck.