Hi knga,
Yes you can play stereo WAV files (44.1 / 48kHz) from the drive into ST3, then stop the playback and start the recording. Simultaneous Qu-Drive record and playback is not supported. Also consider that when stopping a large multitrack recording the drive will take a while to write the files to disk, i.e. you wouldn’t be able to start stereo playback immediately. Should this be inconvenient for your use, or should you need to fade in / out music whilst starting / stopping a recording, I suggest you use an alternative music source, or a combination of Qu-Drive and USB streaming. For example you can play files from the drive whilst recording to the computer, or play from iTunes / Windows Media Player whilst recording to Qu-Drive.
Hope this helps.