New A3 / A4 format printer required... What's the best Performance and Value

Our trusty old HP5000 has clocked up just shy of 600 000 plots over the last 4 years (including weekends thats about 410 pages a day) and is getting just a bit tired and getting serviced about once a week now which isn't very economical. Unfortunately it has only 4MB memory (should have been upgraded a long time ago I know), but it has been pretty robust and trust worthy on the whole.

Our requirements are the following:

A3 and A4 format printing with bulk trays
Lots of memory (plots up to and over 100MB are common)
High Page per minute capacity
Plotting from AutoCAD, PDF, Office and the Net
Medium High B&W resolution 600-1220 DPI??? (All our outgoing A3 drawings are printed from this printer)
Robust and Reliability a must
Readily available Cartridges (Darwin can be painful to get anything that isn't the Norm)
Relatively Low Cost per Sheet.
Low Capital Cost if possible.

What machines are people using and would recommend, what should I steer well clear of?

Cheers,

Daniel.