Here's a very short video demonstrating sample playback on a C64 at 44.1KHz / 4 bits using a SID 8580. Due to size limitations, I was limited to 60,000 4-bit samples.
Because I used the Commodore 64 model with the SID 8580 in it, the audio output was so very quiet; i had to add about 30 dB of gain. As a result the audio was very noisy, and so I have also added a low pass and a high pass filter, to make it slightly more bearable to listen to. I would love to try this out using a Commodore 64 with a SID 6581 in it.