Either that or go with a single 250 watter over the cube. You can either go with something like a nice 14K Bulb that gives a nice blue/white mixed look to me.

The reasons I say go with 250 is you will not be limited, if you decide you want to put a clam in later you're good to go. Also there are many times more 250 watt SE bulbs that go up for sale (very cheap) than any others that I've seen.

Just a thought.