They work fine with my Powercab, I do have a 2.5A supply though. Having said that the standard PSU will have enough power for at least 1 TXS decoder, maybe more.
As to too much, well, a power supply will only supply the current demanded, up to it's limit, so as long as there's no shorts etc then all will be fine. Anyone using a Powercab should have a separate short circuit protection device anyway as the powercab does not respond very well to shorts .....