Looking to buy a Xerox 51dp or Oce TDS 600. Has anyone had exprience with feature upgrade capabilities of the Xerox 510dp, specifically the speed upgrade ? Our concerns are: 1. Can the 5D / min printer part handle the extra workload the 10D/min speed upgrade requires ? 2. My experience with field upgrades is they are never as good as factory upgrades. Any experiences here ? 3. Given the speed upgrade is about 35% of the price should we just get the 10D/min system in the first place ? Look forward to your comments Fred