Over kill as in too much rock? I don't think so, your setting up a sump though right? You can always have rock down in there. I don't think you can ever have to much rock in the system, display maybe, but you seem pretty good. I have probably over 300lbs in my 110g tank, the more the better, better biological filtration. Just make sure you have good spots for corals. I made my rock look good, but then found out it wasn't good for corals, now I should redo it better for coral placement and not looks. Looks of the rock won't matter when it's all overgrown with corals! I'd suggest korilia powerheads, I know you were thinking about them. I have never lost a fish, never heard of anyone losing one either, and had them since they came out, even with chromis, clowns and firefish.