Manual for the Pioneer DV48AV shows that if Audio Output mode is set to Stereo, then Center and Subwoofer outputs are disabled, and the 5.1 channel front Left and Right jacks act as a second pair of stereo outputs.
If these specs hold true for the DV47Ai, and if the Reimer Sub has high-level inputs, then there's a possible direct solution.
Connect all of your speakers, including front stereo speakers, to your 5.1 group of audio outs, with Subwoofer into LFE connection.
Then, connect your extra pair of Stereo Outs directly to the subwoofer high-level inputs.
Then with Audio Output mode set to "5.1", extra stereo out (and thus high-level sub feed) is disabled, and LFE feeds the sub.
When Audio Output mode is set to "stereo", LFE and center channel are disabled, with 5.1's L/R feeds driving the front speakers, and extra stereo outs driving the sub.
Of course, when your new Oppo arrives, all of the subwoofer options so well covered by Mceljo and more will be available.
BTW, your speaker selection looks fascinating!
If these specs hold true for the DV47Ai, and if the Reimer Sub has high-level inputs, then there's a possible direct solution.
Connect all of your speakers, including front stereo speakers, to your 5.1 group of audio outs, with Subwoofer into LFE connection.
Then, connect your extra pair of Stereo Outs directly to the subwoofer high-level inputs.
Then with Audio Output mode set to "5.1", extra stereo out (and thus high-level sub feed) is disabled, and LFE feeds the sub.
When Audio Output mode is set to "stereo", LFE and center channel are disabled, with 5.1's L/R feeds driving the front speakers, and extra stereo outs driving the sub.
Of course, when your new Oppo arrives, all of the subwoofer options so well covered by Mceljo and more will be available.
BTW, your speaker selection looks fascinating!