Charles -
Earl summed it up - you don't want to cheap out on the printer.  We have found that most assembly related (non-DFM origin) defects happen in the printing process - there are many variables.  The more you automate on the printer, the more you take the variables out of the hands of the operator and strive for some semblance of repeatability and precision.
There is a great deal of attrition in this industry.  Once upon a time, DeHaart was the leader in SMT screen printing as well as in hybrid.  But that was long ago and far away.  I watched DeHaart go through its death throes on several occassions including the last and final one (its last owner is a very good friend of mine).
Get as much printer bang for your buck as you can.  If you are budget impaired and are looking used, consider a rebuilt from the OEM - it will have a full warranty and the best software and hardware upgrades.  There are some very good reputable used equipment firms as well that give good support.  But it helps if the printer manufacturer is still in business making machines and parts.

Phil Zarrow

ITM Consulting 
Durham, NH  USA
www.ITM-SMT.com
T: (603) 868-1754
F: (603) 868-3623
EM:[log in to unmask]