Just to throw a spanner into the works, I have a white phalanopsis that I have had for the last two years, it has always been kept on a north facing window sill without any additional lighting! It has flowered repeatedly, to the point of stupidity, having in excess of 35 blooms at a time that last for about 6 months!

So perhaps you should just leave yours on the window sill and see how it does for a bit without worrying about additonal lighting. I don't think there is anythign special about the window where I have put mine, it faces due north and is in the kitchen. I havn't even repotted it since I bought it and its roots are growing wild, I dare not touch it in case it causes it to become upset!

Good luck!