I think you're right. Sosa is awesome, obviously, and Vaughn has actually looked decent of late and might (small chance) be headed back to Boston, which would give him a huge boost in value. I like Pineiro more than Nomo, but in leagues that count k's the dropoff won't be that bad.
There's a bit of a risk here, especially where Vaughn is concerned, but I think the rewards justify that risk. Go for it!