Ive got a kr91 on my 2ft cube. I love it, great colours. If you got the money then go for it. I'd recommend going to see a tank with one on before though, just to see if you like the look. I know of someone on UR that bought one and then sold them straight away and went back to t5's. Just didnt like the colour.
I personally like it. I cant comment on coral hrowth yet as im still quite new to the game and the tank hasnt been set up too long but I have definetely had some growth from my sps frags under it.
HTH, James