Once I had Mbox Pro 3 from AVID. It had 6 line outputs and 2 headphone outputs. One very special thing is that these headphone outputs could have their own mix! So totally I could have 5 independent mixes. So cool for those, who use interfaces on live gigs.
Current Presonus USB audio don't have this feature. Headphone mixes can be only be paired with main stereo mixes.
Please add this feature if possible in current or future interfaces.