Just to duplicate the thought that you should do your research first. You might regret it later. You might have all the equipment but not have the knowledge yet to know how to handle a problem. I am impulsive as well so I understand your desire to rush. Just make sure you understand how to properly cycle a tank at the minimum.
That said. I wouldn't buy one heater I would buy 2 or 3 smaller heaters. Heaters sometimes get stuck on. By getting heaters that individualy are not strong enough to heat the tank you limit any damage a stuck heater has on your tank. This assumes you have a sump to put them in.
I can't make any more recommendations since the end result of the tank lifestock goals are still in question. I see your new to this forum so after the order is in start reading the ReekKeeping magazines online and the
http://www.advancedaquarist.com magazine. This will help.
Good Luck!