@atmasphere do you care to comment? I think the removal of an output filter for Class-D will be very measurable. I guess when you don't have to worry about compliance testing, anything is possible. @atmasphere what would happen if you hooked these up to a big electrostatic speaker or something like a Magnepan? Aren't these switching at frequencies right in the middle of the AM band and then hooked up to all that wire in the speakers? Aren't those speakers big capacitors? What is going to happen without those filters?
The extra output coils mentioned are only part of the filter. Certainly the result will be measurable, and likely audible as well. As best I can make out, the output filter choke remains. The amp would not function without it!
A zero feedback class D amplifier will exhibit an electrical resonance when used on an ESL; this being the result of the choke inductance and the capacitive load of the speaker. I've seen this resonance cause some class D amplifiers to fail.
I'm sure those series inductors are there for a reason. For example, most solid state amplifiers have a resistor/inductor network across their speaker terminals to increase stability at ultrasonic frequencies. In a class D, the concern is always radiated noise. To this end, with any changes made to the amplifier, its a very good idea to test the radiated noise to the AC line, since that noise can leak into other parts of the system (such as digital devices) and really mess with them. That is why its important to not just meet EU Directives, but to actually have noise figures well below that, since a lot of consumer digital devices aren't that good at dealing with switching noise in the AC power. Radiated noise which might emit from the speaker cables (behaving as an antenna) can also get into other equipment, increasing noise in the system.
Because most class D amps (if designed competently) are meant to meet EU Directives and similar emissions ratings of other countries, its often a Bad Idea to mess with the components in the output filter since they are often chosen for their noise characteristics; for example many capacitors have leads which have inductance; if the inductance is increased you can wind up with parasitics, which in turn if they don't mess with the amp directly can mess with other parts of the system.
Put another way, reducing noise in a class D can have a very direct improvement on how it sounds!