a biig reason for 8 outputs is that no matter what you're doing at home there may very well come a time where you have the opprotunity to take your computer to someone elses studio, equipped with genelec monitors, neve console, and lots of lovely outboard stuff...
8 in 8 out is just flexible,, if at home you only use stereo out that's cool, but when it comes to mastering you might do that somewhere else.