Quote Originally Posted by televisor
I'm going to have to rethink the lighting, I'm now torn between an HPS light or going with several CFL's.
Both. Use the CFLs for vegging and the HPS for flowering.

Quote Originally Posted by televisor
What's the heat difference between say a 400W HPS and 10 x 40 Watt CFL's ?
I don't know exactly, but I think the HPS will be significantly warmer.
You will be able to get CFLs closer to the palnts for sure, but the CFL light is less what the plant needs in its late life stages.
You are going to have to ventilate either way.