I remember that. Good old non-linear Paula 
The other effect you need to emulate properly to get that unique Amiga sound is the sample-rate aliasing, which might be slightly trickier to get right. I've always thought that ringing sound it adds to things played at low playback rates sounds a bit like what you'd get via an aural exciter.
PC sound cards work by hardware mixing the sound to a fixed output rate (44KHz or whatever). The Amiga was unusual in that it worked by speeding up and slowing down the individual samples. This means the aliasing noise changes with the pitch the sample is played at and thus becomes part of the sound.
Mixing players may inadvertently recreate this if they are not smoothed but it's likely to be a slightly different effect.
To recreate this effect could prove challenging. It needs to be done in the sample playback routine. You'd really need to create a a virtual instrument to do it properly.
OTOH you could just use an Amiga.
...which is exactly why I was asking about software that does 8-bit non-mixed sound.
