One light over a 75 will work too, but it's going to look uneven.

http://www.swt.edu/~xp42012/2001/55g...-september.jpg
http://www.swt.edu/~xp42012/2001/55g...-september.jpg
You can keep one 400W MH on the right for the SPS, then keep the soft, lower light corals on the right with your current VHO.