I hope I’m not jumping in here but I’d urge a little caution when considering the output power of class D amplifiers. The best deliver what they say, However perhaps we’re used to class AB amps with transformer, rectifier capacitor power supplies and output stages with very little current limiting. These amps would happily deliver power into low impedance speakers until the power rail slowly begins to sag and we hit voltage limit. With class D amps and switched mode power supplies the limit is a hard limit. First off the quoted current limit is a typical peak value not the guaranteed limit of a unclipped sine wave. Secondly there is a thermal limit to the module and its assembly. The ability to dissipate heat may be restricted in some constructions. The class D amp may very wisely decide to shut down if it overheats in a low Z load. Lastly a SMPS will shut down quite sharply if excess power is drawn.
Now this would be OK perhaps if 4 Ohm speakers were just that. But look at some of the better speakers on the market - here is a review by
@John Atkinson in Stereophile of the KEF Blade 2 meta where he measures the load presented to the amp.
Sidebar 3: Measurements
www.stereophile.com
This drops to 2.8 Ohms in the mid bass region where all the audio power is. In fact many 4 Ohm speakers behave this way.
If you talk to BoXem or March Audio they would recommend the use of amplifiers employing the 1ET7040 module if you want voltage clip to be the limiting factor for such a load BoXem suggest a 3 Ohm limit for the 1ET400 modules for instance If you want voltage clip to be the limiting factor.
But let‘s not get too obsessed here - I drive a set of KEF Blade 2 metas with a March Audio P501 (7040 based) and I hit an unpleasantly loud peak SPL of very approx 110dB at the listening position with the DAC set at -10dB or approx 25W/8 Ohm. So perhaps this all doesn’t matter too much anyway!