Two small turbos will have blistering response and awesome low end torque, but may fall off on the top end before they really make serious horsepower. Well, torque is what has a tendancy to break things, not horsepower, so lets shift gears a little here.
Any established low end torque number limits on this motor stock? If I got a turbo (or built one), I'd be much more interested in quick spool and low end, than top end.
The best part about hopping up a stock V6 is you can get them all day long for 2 grand or less with less than 30K, most likely easy miles on them. vs 6 grand for a 5.0 if you happen to blow it up.