I just set up Helix with a six pack of blades and as they run all their boards on PXE boot you may discuss the on board LAN process needed to make that work, it is not neccesarily straight forward,
I do on occasion get boards and chips at good prices right now it would be ECS L7VMM's for four boards, xp2200's retail fan and 128m crucial pc2700 400w powmax PSU is about 190 that includes shipping them. They are assembled and burned in. I do not know however if the LAN is PXE bootable but I can ask.