Battery and alternator upgrades can be figured out like'a this:
Battery will be your tank of water, and the alternator will be your source of water. The faster you draw water out of your tank (battery) the faster you will need to replenish it.
For the most part you always want more power (amps x volts) then you need. So lets say you have 4 100W lamps you want to run on your rack that means you need 400Watts of power to keep them on. If we change the Power = I (current) X V (voltage) we get: 400W / 12.0v = 33amps of current draw.
Your stock alternator should put out close to 100amps during idle so if we consider we have about 80 or so amps of power free to us (on board vehicle components use up some of the current the alternator kicks out) that gives us about 80amps X 12volts (approx.) = 960watts of total power possible.
Personally I wouldnt like to draw this much continuously out of a stock alternator but technically it is possible. When pulling this kind of power continuously you must be watchful of wire sizes (all wire is rated for certain max currents...you always want fuses to blow and wires to be safe, I overate all my wires ran to my lights and fuse them to just slightly more then they need (ie. light needs 15amps I fuse to 20amps....and I make sure my wire can take 30 or 40 amps without damage).
Hopefully that gives you someplace to start. If you have $$ burning holes in your pockets, a mean green alternator, upgraded battery cables, and a nice gel cell battery should be an awesome setup for power hungry lights and an amp guzzling winch). There is so much more to this then I have posted, but feel free to ask questions, volts and sparks are my profession and I do love educating anyone that listens.
....I also dont mind being corrected if someone finds a slip-up.