A Quadra with a PPC upgrade is going to cost too much. Better to go with a 7100 or 8100 machine as they haven't really caught on with collectors yet. The soldered in 601 combined with the inability to run OS X even with a G3 upgrade makes many people avoid them like the plague. The later PCI Powermacs manage to steal most of their thunder since you can take them so much farther than the Nubus machines. I built a Quadra/PPC machine when the parts were still available and cheap, but if I had to do it again today I'd just put a 7100 motherboard in my IIvx case.