If you want pure class A and high power you need a push/pull amp. While very rich class A no push/pull amp stays class A into all impedances at high power. Only a single ended amp(which can only be class A due to circuit topology) is ALWAYS class A and they are almost all low power.
Then again an amp that is say class A up to 30 watts is almost never out of class A and if it is it's for mili seconds mainly> For instance the 30 watt calss A Pass amps are 30 watts class A to 30 watts but then become class B up to around 75 watts(why he calls them 30 watt class A amps. If I recall correctly(someone may know better) if a push pull amp is class A at 8 ohms at a given power it stays class A only at lower power into lower impedances.