The wiring is 4 wire the same as on most machines, motors come in 4, 6 or 8 wire to enable them to be wired differently for different applications. For CNC use generally only 4 of the 6 wires are used & on an 8 wire 2 wires will be joined giving you 4 connections. This thread will help explain it better than I could

http://www.mycncuk.com/forums/steppe...-diagrams.html

The system 48 has nema 34 150oz 6 wire motors but the black & white are not connected leaving red, red/white, green, green/white to connect.

I;m not an expert when it comes to these sort of things but I have gone for 3 separate drivers & a BOB rather than a control box with it all built on to a board, reason for this was firstly I believe it's easier to upgrade if I want to at any stage & secondly I thought it might be less hastle if something needed replacing because of a fault. Pretty sure there was quite a low voltage limit on the control boards I looked at as well, something around the 30v mark I think although that might have changed or I could easily have missed something. No idea about hand controllers, don't have one & I doubt I will ever have need of one.
Power supply will be dependent on what motors you have or intend to fit. The original motors run off a 24v supply & the spindle from 115v ac. I already had a 36v power supply which will be stuck in but that's about the safe upper limit for the original motors. Long term they will be getting changed for nema 23's that I already have which will be operating at approx 68v from a power supply I built with some help from someone on the forum.
Motors, drivers & power supplies all really need to be matched to give you the best performance so before buying anything you need to decide what you want to do & what sort of budget you have.

Is the machine working ok at the moment? If it is them why change the electronics? I have done mine because I got the machine as spares or repair with a fault on the motherboard.
The other thing you need to think about if you are going to change the electronics is the software, That will need to be changed as well. The system 48 runs on gerbers own software which uses their own version of gcode. You would need to run something like mach3 or linuxcnc to control the machine & a cam package to create the gcode. If they are a sign company then they will already have a suitable vector based program for design work.