Is Bi-Amping really worth it?
As always it depends.
Most just use an AVR and have spare channels they can use for Bi-Amping.
The problem is you only have one power supply that is limited to a specific power output.
So in this case, you are not getting more power to the speakers you just splitting the power you had with single wiring. With a lot of AVRs, it is even less, as they limit the power when more channels are driven, to prevent overheating. (e.g. going from 2x100W to 4x40W)
The fewer channels are driven the more power you have per channel.
Just use one channel per speaker and you will be fine.
What about external power amps?
This can make much more sense. With a separate power amp per speaker or frequency range (one amp for bass and one amp for mid/high), you can definitely benefit from lower distortion and better driver control. The amp basically needs to work less and will be operating in its sweet spot power range.
Does it have a benefit over one bigger beefy power amp? Not really, but as always there are many variables that make sound, so it absolutely recommended to experiment and find the solution that fits your personal preference.