Just received my iFi S/PDIF iPurifier one week ago [Music Direct] to matrix with Chromecast Audio puck and Schiit Modi Multibit DAC. Following manufacturer suggestion I plugged it straight into the coaxial input on the DAC and used a Sys. Concept mini-toslink - toslink cable to couple with the CCA. Straight out of the box I was able to retrieve more detail from familiar sources. Looking forward to what continued use offers.
I picked up a couple of CCA this summer and was caught off guard at the upshift in performance it offered in my system. It's still the weakest link but like the OP I'm interested in tweaking it out before exploring other [more costly] options like the sonore microrendu / sonicTransporter / roon. Since the acquisition of the Chromecast Audio I've made a number of system upgrades; Schitt Modi Multibit DAC, PS Audio Ultimate Outlet, JJ 2A3 power tubes, Sys. Concepts digital cable and iFi S/PDIF iPurifier reclocker/jitter filter. Couldn't be more pleased with the performance and bang for buck value the Schiit Modi Multibit provides IMS.
Until the iFi stabilizes the full benefit won't be realized but straight out of the box I was making unexpected discoveries from familiar source [pleasant discoveries]. For my 9k system it was easy to appreciate where the extra $800 [total cost of all 5 upgrades] went. At this very early stage I'm unable to measure the value of the iFi but thus far IMS it's not a component I would suggest is critical to the performance of the Multibit.
The iFi reduces the noise floor even further, something that wasn't lacking in my system previously. While sibilance wasn't minimized to the level I was hoping it was reduced. Overall there was a greater cohesiveness to the presentation that made you rely less on the suspension of disbelief to lose yourself into the music. You're able to pick up the most discrete sounds that appear out of nowhere - spooky. Admittedly, some of these are unintended like when you can hear the bus passing outside of the church on The Trinity Sessions CD by the Cowboy Junkies. Chairs creaking, conversations between musicians, foot steps. Unreal. With my Moth SET amp and Silverline Sonatina speakers much of this was in play before the acquisition of the Modi but it does take it to a higher level. The supplied PS is plugged into the Hydra PLC.