my BBox setup came with a 125W. I replaced it with a 200W and continue to have fabulous results with this. There is more heat but that is not a problem for me. My seedlings vege out with very short nodes and full robust development. I expect that I will need a replacement soon, so I will probably pick up a 250W or 300W (from HD if they have it here) .... my constraint remains space and specifically height (need for stealth) so this system right now works very well for me.