Well Said
Bearing in mind that this is a communications receiver, and not a high-performance BOSE AM/FM system, you might try (when feasible) upping the AM bandwidth to the maximum of 15 KHz. You might be able to do that in the AM broadcast band--- it would certainly be more difficult in the shortwave bands, when stations can practically by on top of each other. Once again, being a communications receiver, there are no compensating Bass (Or Treble) controls.
This is one of the shortcomings on a radio which is designed for the communications enthusiast as opposed to the audiophile.
One cannot expect quality AM audio from a 6cm shallow speaker, but given that the AR-DV1 audio quality seems very acceptable overall.
As you say, 15khz is essential for signal on the AM broadcast band via the AR-DV1, and it is important to switch NR off too.
One cheap alternative for those who do not want to add an external speaker, is to simply connect the radio to the P.C. and use its sound card, via a standard stereo 3.5 mm cable and the audio socket at the front of the receiver. Naturally that depends on the quality of the computer's speakers too. With many sound cards it adds the ability to control the tone.
The bottom line is, as you so rightly point out, this is a communication receiver, and compact size means a small internal speaker.
As a final comment, one of the 'unsung' big leap forwards in communications is the incredible improvement in small speaker design and performance over the last 20 years. Even the tiny speakers in mobile phones produce good audio. Being ancient, I can remember when a 3 inch speaker really did sound like a tin can, lol. However the Laws of Physics can only be stretched so far, eventually "size matters".