OK, it's been several weeks and there have been a flurry of updates. They will be outlined in a few posts to avoid getting too wordy in any single post.
Why so much time and effort spent trying out all this stuff? Long one short, I did something to my back so was pretty much spending time on the couch. Might as well make use of the down time, right? Luckily my back has been getting progressively better each day.
Unrelated to the Allo products - the generic (unmodified) Chinese TPA3116 (powered by a laptop power supply) was replaced with with a Texas Instruments TPA3155 evaluation board. The new amp is running off a 350 watt, 7amp, 48 volt Mean Well switching power supply. It's a pretty amazing amp for what it costs and really outdoes the generic 3116 amp. The bass is more textured and the mids and treble are cleaner. Had to give the amp some real burn in time, though, as it sounded pretty hot at first.
The music files have been moved from the upstairs computer (connected through wireless) to a self powered USB external hard drive. There were too many drop outs and slow downs with the wireless and listening tests showed the local drive sounded better. So the music is local now.
After trying a lot of things that didn't help fix the wifi issue Tim @ Moode posted about wifi issues caused by the Kali. Evidently the oscillators on the Kali are too close to the wifi antenna. His solution is to add some distance between the Pi board and the wifi dongle. So a 3" extension was put between the antenna and the Pi and there is a real speed increase when using the web browser. It's not been tried with streaming tunes, though, but it's really improved the speed of the music server interface.
Even with the music local there are still dropouts in the music from time to time - but it isn't frequent. Increasing buffers generally fixes the glitches but also changes the sound a bit.
More to come ...