I'm a little confused by your question, but I'll take my best shot at answering it anyway. First, the R-15PM is not a media player. You cannot just plug a flash drive into the USB port and play MP3s. The USB is for connecting a device to. So the supported audio formats will be determined by the device the device you connect to it, not the speakers themselves. So if your PC supports playing FLAC then so will the R-15PM. Second, you are correct about Klipsch being a little vague in the specs on the R-15PM. Best I can tell the DAC in the R-15PM supports 24-bit, 96 kHz audio. Which is better than CD quality, but not as high definition as the 192 kHz DAC in The Sixes. And lastly, the R-15PM should work with any device with support for USB audio. Windows PCs, Macs, and Chromebooks should work out the box. iOS devices should work with the correct adapters. Android devices are a toss up, but most device running Android 6 or later should work. Hopefully one of those answers was the one you were looking for.