just buy yourself a Coralife super skimmer and be done with it....muwhahahahahahahahahahahahah
::::::jabs Eric in his manly man man ribs:::::::::
you know, the more skimmers in the sub $300 range I see the less I dislike the super skimmer. I still wouldn't recomend it in a tank this large or with someone wanting the best, though.
Eric's right on about differences.
As far as what light to go with, there is little difference in most of the units that are 72" halide/T5 combos and the prices are pretty close. The real choice is if you want to go retro, pendant or 72" pre-fabbed. Not knowing your tank its tough to say for sure which would be my choice. If your running a hood you may have to go pendant or retrofit. The time to ask the questions on the lighting is when you go to change the bulbs. Lots of data and opinions on bulb choices.