I can state with unarguable certainty that both the ULA-A4x350 and the ULA-A2x700 are NOT a pure class A amplifiers if the specs on the website are accurate. Class A amplifiers have a maximum efficiency of 25% (mind you that's maximum, so most will fall even below this level of efficiency). So what type of current draw would a 1400w RMS amplifier have on an electrical system ? Well, if we very favorably assume that the efficiency is indeed 25% and it's operating on a steady 14.4V electrical system, it would draw a continuous 388A. Not during peaks. Not only a full volume with sine waves. CONSTANTLY.
So, it's pretty easy to reasonably demonstrate that the amplifier does indeed at some point operate in something other than Class A. Now, it's entirely possible that the amplifiers have what is called a "high bias". Which essentially means they operate in class A mode up to higher levels of power than what most other class A/B amplifiers do. Some examples of this would be the old Monolithic amplifiers. A more recent example would be the Tru A Class, which operated in class A up to 25w per channel (then switched to class B).
A simple tell here, and for any class A/B amplifier, is the amount of idle current draw. Since we know that class A amps will continuously draw full power from the electrical system, even at idle, the amount of idle current draw will represent the maximum amount of power the amplifier can supply before falling out of class A operation. For example, if the idle current draw was 2A, with our knowledge of 25% maximum efficiency and an assumption (if we don't know the actual voltage) of an input voltage of 14.4V, we know that best-case-scenario for class A output is 7.2w total (for a 2-channel amp, that would be 3.6w per channel).
So, what is the idle current draw of those Critical Mass amps ? Because I highly doubt it's 388A //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif