Amiga is just a straight 28khz 8bit DAC x4 simple. You don't need to emulate it you don't need to do anything to it.
The only difference when I play my mods today on my PC is because I use a 100% digital system from mod playing application to amplifier generating the music is a lot less line noise (zero) or distortion (well it is a high grade AC3 Sony)
As for the double pal/productivity mode hack for the 32khz screen modes...well few people could use those modes on their Amiga and games or demos would run slower if used as it massively saps CPU time doesn't it? So dead end really in reality unless you want a blank screen when playing mods.
There is nothing wrong with 8bit DACs though, Bob Yannes who designed the SID chip also designed the Ensoniq Mirage 8bit sampling synthesizer and the stock machine sounds so good the band Inner City used pretty much just that one synth and a drum machine and sequencer to produce their first album in high quality.
