For a 75gal an Emperor 400 will work ok. But remember the unlike fresh, Saltwatch tanks need a lot of turnover. About 10X per hour. So for a 75gal tank you need that water to be filtered/skimmer at the rate of 750gallons an hour. On my 75 gal I have an Emperor 400 hanging on the back, My skimmer hanging on the back, I have a Rena XP3 under the stand. and three powerheads in the tank to circulate the water.
The emperor 400 I run the carbon pads and my phosphate media. and the Rena XP3 I run some more carbon, Nitrata zorb, and the different sponges to keep the water totally clean. That tank has been up for 4 plus years with out any problems. As for the lights, I would get a set of T-5's. They will handle most corals you may be interested in.
As for the water in the box. I would say NO NO NO! Saltwater needs to be airated, and unless they have a power head running in that box, I don't see how that could be. Saltwater looses its benefical strengths after sitting a while. usally in a week or two. and that is if you keep it airated. You have no ideal how long that water has been sitting in that box.Could be six month, a year maybe longer. If I recall right, a few weeks ago there was someone on here that was haveing problems with their tank and that is how she set up her tank.
Saltwater is not that difficult to mix up. and if you are nervous about mixing it yourself then go to your LFS and buy the saltwater they have. (Bring a couple clean big jugs).
You will need extension cords, timers, zip ties, test kits. About 110 lbs of live rock and 110 pounds of sand. Heater, vinyl hose about 4 feet for syphining the tank, a few five gallon buckets. Turkey baster. That is all I can thing of right now.
Just a note: They have a very good, and active classified board here so you may be able to find some of your equipment right here. Alot of the time the equipment is in good shape, Just once the saltwater bug bites you, you always want to go bigger, and we have to finace our addiction somehow. Check them out.
