Just "upgraded" from 2 AC110's, 2 AC70's, 2 Rena XP2's, and a 304 Fluval on my 125, and added a 220g cap. w/d with 1100gph @3ft.
Lots of gph, lots of media cap., lots of current, and lots of energy consumption.
I'm starting to think that maybe there really is such a thing as too much, or at least a point where more makes no difference..
The w/d really did not increase the water clarity, and the tank's not stocked heavily enough to need the extra bio, so the only thing I can see so far, is the "bragging" rights to say I've got ~3550gph (~28.4x) turnover in the tank.
Not worth it to me. Probably be scaling back down to the point where I see a difference in quality/clarity of the water.