Thanks to everyone for the input. I'm going to forget about the substrate
heater for now, and "invest" more in the lighting.
Currently I've got a run of the mill fluorescent hood (via Petsmart). I'm
thinking it would be best to upgrade to HO fluorescent. What's the best way to
go about this? Should I purchase a whole new lighting element or can I upgrade
the one I've got?

Thanks so much for all your help. My LFS is not nearly as knowledgeable as I'd
like...

Danielle