I have an Emperor 400 and an Emperor 280 on my 75 gallon. (and they both use the same filter cartridge so that is convenient)
Ordering fish online can get pricey because of the overnight shipping.
You can end up paying more for shipping than the fish is worth.
Look through the online yellow pages for aquarium supplies. Even if you have to drive an hour to get to a good aquarium store it is worth the trouble.
You can do alot with a 75 gallon. I suggest you get it set up and do a fishless cycle while you consider stocking options.
Then decide if you want a peacefull comunity tank or a more agressive cichlid tank or predators or, my favorite Plecos (you can keep a few plecos with most other fish as well but research the specific species)