It's indeed a bit of overkill i guess. As you'd need 6 outputs per panned audiotrack of your DAW. Ouch! Is gonna cost a lot in D/A convertors...
You best look out for a mixing system which has 5.1 panning. I know www.tonelux.com has units for this, but i'm not sure if the system also actually sums, or if they are more like mixerchannel strips which still need a summing bus. Paul Wolff hopefully jumps in to clarify.
If they don't sum, you can still look for a summing system like Folcrom to sum each of the 6 surround channels which are outputted by the mixerchannels. But at least you would have saved a lot on D/A convertors.
For example: Say for 16 DAW audiotracks, you'd now need only one DA16x (around $3000, Apogee taken as example as it's prolly one of the cheapest solutions), instead of six (around $18000). Saves you the hassle hooking them up, and also $15000, from which you'll have rather some money left even after buying a system like Tonelux (or similar).
Well, I think somebody ought to try it. Not everybody, but somebody. It seems entirely unnecessary to me, but I'm sure it would really kick ass for some special gearslut who happens to have six ears. Personally, I think stereo is overkill.