All in all, I agree with Patrick (it is not often he hears that from me

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The print engine is an important aspect of the decision making process. But equally if not more important is the decision about which DFE (digital front end) to go with.
I have had considerable experience with the Xerox DocuColor 6060 and 5252 and some experience with the Igen. All are excellent products. What I have seen of the 7000 and 8000 is that they have minor differences and improvements over the 6060.
Keep in mind the types of paper stocks, stock changes, coverage area, color precision (specifically with PMS colors), etc. that will be required for your targeted digital print work.
The Igen provides the best digital output I have ever seen; however, to achieve that requires considerable resources and expertise. It is not as simple as open the file and click print. Operators need to understand print, equipment mantenance, color and all of the related software applications.
Also, consider the typical length of runs, sometimes a better decision is multiple devices (slightly slower) over a single device that might be faster. Multiple devices could provide much needed redundancy (digital presses do go down from time to time) and better workload balancing.