Personally I think the Powder Snake is better than the Sickstick. Same shape, but a more traditional core and flex profile. Just more oomph in a slash or popping off pillows.
Your 157 Nitro is going to be more than fine for 140lbs. As long as you've got a decent grade to the mountain you're at even if it dumps 4 feet that board is enough. Keep some speed and you'll plain just fine.
Go ahead, drink that kool-aid.
FS: Forum Sauce 142 $200 plus shipping
FS: Flux SE30 $75 plus shipping