If you want actual amiga sound, use 4 channel mode and capture the audio externally.
To me the Amiga sound is what you got on mods back in the late 80's & early 90's. Back then floppy was the means of transport and being limited size meant mods had to be really squeezed. The way to do this of course was use samples sampled at around 8KHz.
This meant they were noisy due to quantisation noise from the low frequency and low 8 bits resolution. However because of the way the Amiga played back samples the noise was in effect retuned for different notes. This has a musical and very distinctive effect to the sound. Then there's the impact of analogue components and the characteristics of the DAC as well.
I plan to record with my Amiga at some point and this is what I want to capture. The lo-fi, grungy, but most of all, unique sound of the Amiga.
BTW I believe there was a discussion on the non-lineararities of the Amiga sound O/P at one point. Is this on line anywhere?