Dual 120 radiators are a better way to go, you can add more components like video cards in the future and still have enough radiator capacity, plus you can run a 2x120 more quitely than a 1x120.
Well yes of course bigger is better. Why not go with 4x120 in the swing out side panel? A single 120 rad in the top would be fine for cpu only cooling though.
I'm straining my brain trying to figure out how, if it is possible at all, to fit a 120x3 rad into an 830. I COULD go with 2 120x2s in the side panel, but I'm a bit leary about putting that much weight on a plastic bracket.