In one of my jobs, all I do is work with printers but unfortunatly I have nothing to recomend under $650. Watch out for hidden costs though! Not all printers have the drum units attached to the toner cartridges and in this case, expect to purchase a new drum unit about every 3rd toner cartridge. Just put drum and fuser costs in when calculating cost per print. It almost always will still come out to be cheaper per print than ink-jet printing but it still sucks when you encounter costs you didn't know about previously. THe best printer I'd recomend to you is a Xerox, I'm not sure of the model but it uses wax-like blocks instead of toner and the prints are amazing!
Keep On Truckin!