I don't know where the "pro" bit comes from, but the 6501 is an updated 6500. Some changes are cosmetic, some are not. Search on this forum and you'll find a description of the differences (one from me, a couple from others).
Key Steps To Making Your Workflow Profitable
The most profitable print shops remain agile and respond to their customers’ demands while keeping inventory levels at a minimum, decreasing the amount of time from order to delivery and making it easy to do business with.
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