Use 12 gauge wire (which is rated for 20 amps) and use a 20 amp circuit with the Ranco plugged in to a 20 amp receptacle.
1,800 is the max load for a 15 amp breaker, but you never want to run a circuit at its max capacity. The rule of thumb per the National Electrical Code is to run no more than 80% of the circuits max capacity, so a 20 amp breaker on 120V will have a max of 2,400watts, so 2,400 x 80% = 1,920...which means you can safely run 1,800W of heaters on it (you can actually run up to 1,920 watts safely).
If you use only a 15 amp breaker, you are always going to be at the max threshold for the circuit and you could run into issues with your breaker tripping. I would also be sure to plug it into a receptacle rated for 20 amps. I was using a 15amp receptacle on my setup (I run a ranco that controls six 300w Jagers for a total of 1,800W) and I noticed a few months ago that it had burn marks on it. That scared the heck out of me especially seeing Chaidan's thread where his house recently burnt down. I swapped it out for a 20 amp receptacle and so far so good. No more burn marks.
In any case, a 20 Amp breaker using 12 gauge wire (12-2 Romex) with everything plugged into a receptacle rated for 20 amps will be the safest way to go.
Bummer you are not closer, I would have hooked you up with the 12-2 Romex...I have about 200' leftover from remodeling my kitchen.
Edit: Whoops, you beat me to it. What your electrician said. =)