I have tried an IBM 1572 and HP4350tn with envelope feeders. In both cases the manufacturer stated that printing envelopes would not degrade the performance. Once installed the speed dropped to about 10-20 ppm. Both times the manufacturer tech support says, "Oh yeah. We slowed the print speed on envelopes on purpose". IBM was to save the fuser and HP was to stop smearing of the print. $2000-2500 is the budget. Anything from 40 to 50 ppm would be fine but the envelope printing needs to run at the stated speed. Any ideas?