if you think covering the whole tank with Led is a bad way to go, just use Evilc66's PAR38 spotlights and your problem is solved, though for a big tank it won't be cheap but then again even a DIY setup on a large tank still isn't cheap
i will be using only PAR38's over my 200g DD when it gets up and running, but i'm 2 months away from getting my lighting setup over my tank, but i will have a ton of pics after i do
i've only seen a few big tanks with Leds over them, the color and growth are there from what i've seen, the only thing that isn't proven is how long the leds will last, but then again since noone has run any single Led fixture for 8-10 years straight it's also going to be hard to get that answer until a decade from now, lol
All the pics i've seen for leds are promising though and i definatly see our hobby heading in that direction