Do I break down or do I refurbish?

the Quad core Definitely have value. The dual cores can sell for some decent money.

one of my clients are the people that buy the bulk government auctions and they refurb the computers... slap a 40 or 80 gb hard drive in it and sell them with a stock keyboard and some random decent looking monitor.

the Dual cores go from anywhere between $70 to $140. They use an auction site that is pretty well known around here though. They pay a commision to them.

Also they are certified refurbishers from microsoft.

That being said...
you need to be able to find an outlet for the computers. Something is only worth as much as someone will pay for it.