This would be bi-wiring not bi-amping and it might not be advantageous at all.
To see if the wiring configuration of the receiver is in series or parallel, try hooking up the woofers to channel A and nothing to Channel B. Then select A+B and see if you hear anything coming out of the woofers. If you do, the speaker jacks are wired in parallel you can use both sets of speaker terminals as you intended. How much of a gain you get from this, if any, may not be worth the added cost or trouble. The only way to find out would be to try it out. Either way, it wouldn't hurt anything. The setting would still remain at 8 ohms.
If you do the A+B test and you get no sound out of the woofers, you shouldn't use both sets of terminals for the speakers. That's because the outputs are wired in series, which means that the signal would have to go from the receiver out to the woofers, back to the receiver and then out to the tweeters. This would create a time delay with increased signal smearing.
Hope this helps.... Sean
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