Media Center's default DLNA server converts everything to mp3, I guess to make sure it will always play. Unless I created it myself (which I don't recall doing), there's also a DLNA server named "Audiophile 24-bit DAC". I use this to play to my Muso Qb, with the audio mode set to "Specified output format" , the format set to PCM 24-bit, and DSP studio's output format set to convert everything to 44,100 Hz with the exception of 48,000 Hz and 96,000 Hz set to convert to 48,000 Hz. That way all my files play, whether they're hi res, DSD, or standard FLAC. My Muso is the generation 1 model, so if yours is newer check the specs to see what formats it supports.
Once you've got the DLNA server configured, right-click on the Muso under Playing Now and associate it with the desired DLNA server. Media Center is really very good here, so it's a pity the default converts everything to mp3.