I think if your on a tight budget it would be a huge ass waste of money to have seperate main and LAN rigs.... You could build one bad ass super computer for the price it would cost to build two slightly-better-than-average computers.
It would be like buying a car to drive in the summer and a 4x4 truck or suv for the winter when you could just buy a Subaru WRX that is bad ass and faster then both of the other vehicles in the winter and summer. Hope you guys like that analogy, hehe. I know theres atleast a few WRX lovers on this board form seeing peoples sigs!