Id say 178, because even though you way 125lbs, the invader is a super soft ski. You will love the 178 much more especially if your going to centermount, which i dont see why you wouldnt. 178s for sure bro, you wont regret it believe me.
As long as its not the 151 you'll be fine. 7 cm isnt going to make much of a difference at all, and since the invaders are 100% symmetrical, it'll make even less of a difference.