No. There is no difference in heat output between same wattage bulbs. A 250w SE and 250w DE will put out the exact same amount of heat.I have heard that the DE runs cooler than the SE, any truth to that?
Yes, a HQI ballast is magnetic and they overdrive the bulbs and use more power. The ballast in the package you linked to has electronic ballasts. They will fire the same bulbs as a HQI ballast, but not overdrive the bulbs and not use as much power.I also read that the HQI ballasts use more energy.
This is what I had in mind..
IceCap 250W Double EndedHQI Metal Halide Retro Kit - AquaCave
They come with a regular parabolic reflector. I really shouldnt upgrade to the LumenMax Elite..:| Already spending way too much money on skimmer and pump........Will those work "ok'
Like Ryan said, that setup will work fine. The reflectors aren't the greatest, but they will work. I would also suggest the same setup, but the SE version. You have a little bigger choice of bulbs in SE when you need to replace them down the road. Besides the selection of bulbs, there isn't much diff between the 2 using their standard reflectors.