If you do a search on the site you will find all you need to know. I like Won Brothers for larger setups such as yours. They have a seperate temp control so you won't need to be fiddling around in the water adjusting temp. Get a grounding probe for your tank while your at it. Protect your investment.
I use Rena...It's heavy duty. The only heater I've found (lately) that sells up to 300 watts. But I've been looking at Marineland Stealth lately...it seem interesting.
I have these in 2 of my tanks. I can't imagine a better heater
"An economical heater that won't break. Includes convenient controller outside the aquarium. Keeps your aquarium at correct temperature levels. Stainless steel, submersible heater with remote temperature probe and controller that ranges from 68-93° Fahrenheit in 1° increments."
For an aro I would personally not want a heater inside of the tank. Google the word Hydor.
They make inline external heaters. Don't know what kind of filtration you're using but if you're running a large canister filter it would be a good choice IMO. I have a few of those myself and I recommend although I haven't had them very long. Time will tell if they are worthy of their high pricetag.
Check the Sticky on this forum, and you'll find all you need to know. Also, I generally recommend to use two smaller heaters rather than one big heater.
Agree with Harley. Now that I know you're using two canister filters, one heater on each would be the best way to go if you go for external heaters. That way the water will be heated more evenly and each heater won't have to work so hard. You will also gain the benefeit of having one heater still going if the other one craps out.