I was using two 400w 20k radiums + LED's over my 4x2x2 after having 100% LED's. Things looked pretty good but I've been running 14k Ushio's for the last six months with (3) AI Sol Blues to supplement. I am SO happy with the "Pop" and the growth and color in 90% of my corals. After using a 20k and 14k bulb I would personally recommend going away from the Radiums if planning on using any supplementation. For my viewing pleasure I think 14k is a great base to start with then I'm able to use a combo of Blue, Royal Blue, and Cool White to get the exact look I want through the LED's.
I'm a harsh critic and quick to scrutinize, but I've got a winner now. I bet the same results can be achieved through other lighting combos but the one I'm using now is pure money.