Definitely should work if you run Loop Out to the Duet, then out from the Duet into the Loop In, then Master Outs from your Bozak to your amp. Done it myself this way, albeit with a different soundcard. Just make sure you've got direct monitoring set up on your Duet preferences so that the signal coming in gets sent straight back out again. Judging from pages 33-38 in the Duet's user guide
, you need to do this in the Maestro mixer page. If you're recording in Logic, make sure you untick Software Monitoring in the Logic preferences as they suggest, as you'll be using Maestro to monitor instead.
The other option is to connect the Loop Out to the Duet input, but connect the Duet's output to a spare input channel on the Bozak (if you have one). Then just connect the Master out from the Bozak to the amp. When nothing is connected to the Loop In, the Loop Out acts as a Tape Out. Just make sure direct monitoring is off if you connect it this way, or you'll end up with a feedback loop as you turn up the channel the Duet is playing into.