MAKING USE OF THE VIRTUAL CHANNEL.
At first i thought the Channel Inputs and outputs are not enough but then i tried to route the tracks from the Daw to the Virtual Channel IO by choose one of the Line outputs you can return the signal to one Audio channel from the 8 Inputs and record the Tracks or the sum the way you want.
The Universal Audio plugins are very high defined through Apollos internal Console Mixer. It makes a difference routing through the UAD MIXING console than using it directly in the DAW plugin interface. I just mute the Line Input coming from the output of the Virtual Channel IO and then I canrecord directly into my DAW. In some cases you can save Channelsettings for particular Channels and Instruments and recall by loading the projects.
Thinking about the Apollo 16 but the Virtual Channel are 2 stereo channels. You can use up to 4 sometimes it is interesting to hear how it sounds simultan. After recording the drums for example you can also make one Mastering setting with Shadow Hills Mastering plugin or Precision Mastering plugin and then record it stereo into the DAW. Sometimes it is interesting to buy one adapter with two outputs for the Line to connect the Master LR to the Line Input Channels because of the auxilliarys and bus effects. In complete 6 Inputs needed for this kinda 1 stereo for the Masterout and 4 Mono for drums for example or 2 Mono and 1 stereo Virtual Channelstrips to the Line Inputs 3/4, 5/6 and the Masterout to the 7/8 Input of the Apollo Duo. With 2 of these cables http://www.thomann.de/de/cordial_cfy_03_vyy.htm I can get one more Masterout to record the Tracks of the Mixing console in realtime to the Line input. In this case it is the line input 7/8.
Hope you enjoyed this trick !