Morningstar Tristar MPPT-60
Normally charge controllers are measured in amps -- a very simple calculation will get you close 600w / 12v = 54amps. Running 24v panels 600 / 24 = 25 amps. It is not as accurate as it could be but close enough at this stage. That means that when output is less than perfect, which can be most of the time, you might only generate 10 amps w/24v panels, the upside is you can probably generate 1-2amps in the rain.
But there is more, you can run panels at 12, 24, or 48 volts, which means you can get closer to the rated output with more panels. I like the MS product, it would be worth reading the manual on that controller.
This is an American made product, and very well respected.