I have dual subwoofers,
My setup has been cleared with the speaker manufacturer (indeed it is one of their recommended configurations).
L, R, center, sub, and surround RCA out of Oppo and into multichannel preamp.
L and R RCA out of preamp, Y'd.
One Y'd L and R RCA pair to power amp.
Other Y'd L and R RCA pair to subwoofers.
L and R power amp output through speaker cables to L and R front speakers.
LFE out of preamp, Y'd to subwoofers.
The L and R front speakers get full-range from the power amp.
The subs get L and R full-range, and LFE, from the preamp.
This arrangement avoids running the L and R to the subwoofers through two power amps (the subwoofers have their own power amps). This arrangement also keeps stereo and LFE completely separate.
Your mileage may vary, but this has worked really well for me.