converting from 150W to 250W

Agree with Grins on this one.. With the Balasts and Bulbs being about the most expensive parts of any light fixture I'd just buy a 250 to begin with since you don't have an existing light setup.
 
The Coralife Pro light fixture is nice, but if I was going to invest in updating to 250w I would add a canopy and then put in the retrofit like Grins mentions. Just don't forget the cooling fans in the canopy! I think it would be a pain to put the new ballast in the Pro light fixture - are they the same size?
 
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