If you transfer audio over Ethernet then you really transfer data and jitter doesn't apply since data doesn't have time base. Playback program doesn't matter unless it has some kind of processing in it (like upsampling).
Jitter is promptly recreated inside of your receiver when data clock is created for D/A converter. The only thing you can control is ambient electrical noise. Using power conditioners/filters, keeping devices and cables apart and even using better Ethernet cable (since it acts like long antenna for RFI) might reduce jitter. I said might, because your receiver's clock could be the predominant jitter source. As for HDMI - I don't know much about it.
Jitter is promptly recreated inside of your receiver when data clock is created for D/A converter. The only thing you can control is ambient electrical noise. Using power conditioners/filters, keeping devices and cables apart and even using better Ethernet cable (since it acts like long antenna for RFI) might reduce jitter. I said might, because your receiver's clock could be the predominant jitter source. As for HDMI - I don't know much about it.