Get your own 5 or 10lb cylinder at a local welding shop. A lot of places don't actually refill cylinders but prefer to exchange them. If you pay for a shiny new cylinder, it may be swapped out for an old one when you need to get it filled.
JBJ and Milwaukee both offer "all-in-one" regulators with similar pricing and warranties. Some have reported having problems with contacting JBJ regarding warranty issues. You can do a search on either (JBJ or Milwaukee) for some more reading. Plenty has been mentioned on this site about them.
I wouldn't waste my money on a complete system (Tank, regulator, diffuser/reactor, etc) at some of the on line retailers. You can find a system much cheaper if you do a bit of the footwork yourself.
You should check out the sponsors of this site. Some of them offer regulators and reactors and may save you a bit on the shipping if you purchase both from the same retailer.
OK, I can't figure out how to attach a picture, but if you go to the Drs Foster & Smith website and look at the Simi-Automatic CO2 System, maybe you can answer my question. And when I say "you", I mean anyone.
With this system, I would just have to get a canister, and hook it all up? And that's it? What size canister would I need for my 75g?
Please, any help on this would be greatly appreciated.