Pretty much true for the professional grade 3 range. The Honeywell galaxy still has a nice big linear power supply. The panel has 1amp available for outputs, but when you have new style backlit grade 3 sounders like the new excellent texecom x-b, two sounders can take 460mA each, not leaving much for anything else. They do have an alternative to SCB low current mode though.
You can pick up a power Rio for £40 on ebay, which is the way to go with these bigger panels.
One other thing is that if the battery in the sounder goes faulty, then replace it. Regular maintenance would find any issue and having the first sounder as SAB and second as SCB lowers the risk of having a scenario where both SCB batteries go bad causing failure to alarm.