I'll up crgildart's ante by suggesting that a ski over 110 or so cannot be a 50/50 ski, in terms of design parameters, no matter how you may use it. It's too slow to get up on edge, and takes too much leverage to carve. So a few questions: Do you live very near somewhere that gets a lot of powder, and have the ability to take time off to go enjoy it when it's fresh? If yes, then something in the 108-112 range might work.
If no, and the 50/50 comment makes me believe this, then you'll be happier buying a 98-108 mm ski and in the event you are onslope for a serious dump, rent a really wide ski. The number of days you can be there that Alta gets so much fresh that you can't enjoy it on a 98-108 mm ski, you can count on one hand with fingers left over. The number of days you can be there that Alta between storms has mix of firm, stashes of settled fresh and some crud around, an order of magnitude more. So which do you aim for?
Some candidates for a 190 lb guy your height: Bonafide, BMX 98 or 108, Prophet 98 or Influence 105, Hell n Back, Alibi, Head REV105, Cochise. If you can wait until next season, add the Stockli 107 and the Rossignol Soul 7 to your list. Most of those have been amply reviewed, suggest a search. If you want a more forgiving, softer ski that will be more fun in soft snow, less in firm, then the Rocker2 108.
And yes, 178 is too short for a real powder ski if you're 6 ft. Might work for a 98-ish 50/50, depending.