milkman, please forgive me for not answering you sooner! I just now saw this. Sorry.
That's tight with that big old bulb in there, eh?
The more light the better, of course. The 125w bulb will be plenty for those three plants in that space to get a real good start. But then after about roughly four weeks, assuming all other factors are good, they'll have lots and lots of foliage that the 125 watts just won't be able to penetrate. I know you didn't want to hear that, but I know you want the truth. If you have the room for it and the heat doesn't become an issue, I'd add the 2700k bulb as well, when they start to flower. Is it also 125w? You'll also have to tuck your leaves, to help penetration.
Start up a thread with your setup and all and maybe a few pics and let's have a look and see what you have going on! Again, sorry I missed that! :smokebuds: