I learned my mountains slackcountry on 175 GS skis with dimensions of 100-68-?? and loved it!
But the skis are truely horrible when compared to powder skis. See the point? You CAN do it and enjoy it(well, I've actually met plenty of park guys that can't even turn skis with less than a 100mm waste in pow...but that is just sad) but a pow ski or fatter "all mountain" ski will be more enjoyable.
Oh, and I would much rather be on those 68 wasted GS skis for real skiing then a pair of center mount symmetrical noodles. I would recommend waiting around here and other places till a beaten old pair of decent fat skis comes up, mount them not centered since center mounting a ski often(meaning always unless its chopstick type shape) rapes its powder performance, then enjoy them way more than you would the Invaders! Cheap way out!