Envelope printing

Can anyone out there recommend a digital 4-color printer/press that handles envelopes? I can't find any mfr that makes a production quality digital press. Dye-sub doesn't work, because the ink melts in my customer's laser printers. Ink jets are too slow w/no drawer capacity and the Riso 4c press quality stinks. My old low-volume Minolta BizHub did a pretty good job, but the new, larger 6500 doesn't take envelopes. None of the big Xerox machines handle them. There is a co. that puts out an envelope feeder, packaged with a QMS laser printer, but again, the quality stinks. ANYONE HAVE A GOOD LEAD ON THIS?