Whatever you do, I recommend PowerPoles for your outlets. For 12V up to 45A use the red/black pairs. You can get a nice panel outlet (and a bunch of other neat doodads) here:
http://www.powerwerx.com/product.asp?ProdID=1783&CtgID=1681HTH,
A
(For your higher-current lines I recommend you hard-wire them- you're not really going to want to plug and unplug a 250A connector! Oh, and you shouldn't anyway- only unplug and plug high current loads when the supply is off.)