I use a Tunze, i had a Innovative Marine one, but the Tunze i feel is sort of better with the sensors, and it has a siren incase your ATO is stuck in syphon and continuously dispensing.
But a tank that large will require a large DI reservoir, unless your Kalk dosage is significant enough to offset it.
For example, i am dispensing about 600ml of Kalk solution per day on my 150, so my ATO does not dispense much. But if i didn't do my kalk, then i would need at least 600ml of DI water per day on top of what its already dispensing.
I also use the overpriced ReefCan as a reservior, but i could not find a trashcan bin thin enough with the same dimensions of the reefcan, hence why i was strong armed to buy one.