@Bart
LXminis (with two subs), using three Topping D30's in between NanoDIGI 2x8 and a multichannel power amplifier. The upgrade to NanoDIGI + external DACs was a significant improvement as far as background noise is concerned. The three Topping D30's are powered by one 15V power supply.
Thank you for responding and welcome to the forum!
Solved the noise issue by changing the temporary (store-bought) interconnects with some DIY (Belden 1694A) interconnects (I cannibalized from other gear in the same system). They are short, so I had to move everything around too. Different cables or being disconnected/moved/reconnected solved the issue. They are quiet now - both connected to USB splitter plugged into the USB socket on the Panamax MR4300 front panel.
I can say the sound is different - probably better. A little more 'precise', and that can be interpreted as better or less musical. Was fiddling with the 6 filter settings, but not sure if I can immediately tell the difference between them. Maybe after more time listening without the air conditioner coming on/off.
My main goal is to improve sound while reducing the cost of the system. With a carefully-selected streaming source, could free-up the NAD C388 (with BluOS2i and HDMI-2 modules = fully loaded) for sale. The tricky part is functionality and ease of use of a single all-in-one integrated C388 unit.