your zen mini is a good streamer/endpoint but even in innuos’ line, there are better streamers, with better internal noise management, isolation, clocking... so there is better sound to be had, otherwise who would buy the more pricey innuos models right?... question is, with your current speakers, will you notice that much of a difference? we can’t tell you that...
roon users using a core machine plus optical rendu driving its usb out to dac is very very hard to beat, but there are others ways to skin the cat -- none are cheap, many require a number of small boxes and power supplies... gets to be spaghetti time in a hurry
i had gaia into pontus, i did not hear a significant difference in sq from using coax spdif into pontus, but then again i wasn’t using a noisy everyday multi use computer to feed the stream
my sense was, pontus + gaia was $3 grand -- could do better with other gear...the pontus is nice as a 1500 dollar dac... there are notably better in the 3 grand range