crest audio ca series amps employ single toroids on their power supplies but can handle 2 ohm loads very well. it's the amplifier circuit that matters when loading low impedances. china amps use high voltages on their power supplies almost bringing the output devices to their limits, kaya delikado na sila sa low impedance loads.
naglabas din QSC ng powerlight HV, good for 4 ohm loads lang, high voltage kasi sya, also their RMX series with HD, heavy duty good for 2 ohm loading kasi mas lower ang supply voltage but same number of output devices.