Well I started getting all excited about the purchase of the HP3100 thinking of all the possibilities, that is until I called my brother to tell him my plans. He is a service manager for a prepress supply company and deals alot with HIGH END printers. Well he really put out my fire on this one say that while his company is an authorized HP dealer, they are not carrying the 3100 due the various problems tpeople are having with them. I'll need to do more research to (hopefully) disprove this but he says that every trade show its been at this year has got a Z3100 in it with an HP tech shaking his head and throwing up his hands in surrender.
He suggested that I fix the 4000 and if I wanted he'd get me the necessary parts and when I'm ready, he could throw a 7800 my way for cheap.