Yes, upgrading will be a waste. Get the killer DAC. Isolate the iMac from the DAC, and learn how to use Roon. Not all killer DACs are killer DACs. The Mola Mola is. They market it as "DIGITAL THAT’S AS GOOD AS ANALOGUE", but really there is nothing analog that does or has ever come close in the audio world. However, it appeals to a certain target clientele. That does not mean you will like it. However, there will be no value using a super expensive streamer with this product. Nothing the streamer does will make the DAC better assuming you have some electrical isolation. I can't say that will be the case for other DACs. I am sure you will get lots of people saying this is not true, but I also am sure they have never blind tested a product like this with a low cost, but bit proper electrically isolated streamer, and compared it against so called "extreme" streamers. At some point diminishing returns = no returns.