Let me try to explain it this way:
I want to use the two microvees as a stereo pair, essentially to fill in lower-frequency midrange.
The "proper" way to do what I want is to use the Left and Right speaker-level input on each of the subs, respectively, and connect those to the receiver L and R speaker binding posts. Then I should use the speaker-level out on the sub to go from the sub to each of the L and R speakers. Then each sub + orb speaker pair in essence mimics a full-range speaker, with the sub providing an internal active crossover at (I think) 80Hz, providing I program the receiver to treat these as "large". It appears I am nonetheless obligated to use a receiver crossover no lower than 40 Hz, so each of the subs will only be used in the 40 to 80 Hz range. (My other sub does LFE+L/R down to 23Hz, so the 40 Hz crossover isn't a deal-breaker.)
Basically, it doesn't sound great, because the (fixed!) 80Hz crossover frequency is too low for what I want to do. (If it was my only sub, I completely understand why it shouldn't go higher than 80 Hz, but since I want to use these as pure-left and pure-right channel, it would have been nice to be able to crank this crossover up to about 120 to 150Hz, to better fill in the lower mid-range). The lower-level inputs on the sub, however, have an adjustable crossover that goes way up to 200 Hz, so I had hoped to use that instead, while leaving the orb L and R speakers directly attached to the L and R binding posts on my receiver.
If I split this off from the receiver's LFE out, I won't get the stereo separation I want for the higher-frequency bass.
I think in order to get the L/R pre-outs to work, I need to tell it I want to configure the system as a 7.1, with two sets of front speakers.