The short answer is yes, your system is good enough that cleaning up the jitter from your source will make a difference. I would qualify that with a comment, though.
Doing this would then make your DAC the weakest part of your system (in my opinion). If you then look to upgrade your DAC in the near future, there are enough interesting options coming out that you might not want to keep using the Sonos as your source. For instance, I have the Cullen mod on my Sonos, but will be abandoning it once the Bridge is available for my PS Audio Perfect Wave DAC (same functions as the Sonos but with high res capabilities). More and more DACs are being made and designed with this in mind, as well as better and better USB connected DACS (especially the asynchronous ones like the Benchmark DACs).
Before you splurge the $600 on the mod, consider your path for your next upgrade or where you want to go in the future and that money may be best added there. If you are into classical, the amount of music you can get on high resolution downloads and HRx formats is growing fast and that is something the Sonos hardware does not support. If you have ever heard high resolution recordings - especially on classical pieces - they almost always make a marked improvement in staging, openness, and bloom.