I can just concur with the what others have already stated - the vast majority of SQ improvement (for streaming use case) is there also when using the old network card, it is the switch and the DAC-connection that is the key, the network card to a much lesser extent.
So - using the old network card is a very easy fix while we wait for replacement bracket.
(I suspect that some of the magic is lost when playing local files though - the offloading of processes from Extreme -> Switch depend on the new network card - I have not yet verified).
Added bonus - I can look forward to yet another upgrade when the new bracket arrives and I can deploy the new network card!
Until then - I'll be lost in streaming...