A long time ago I used a bi-amp setup with two Rega amps into a pair of Proac D-28. The improvement over using one amp was very noticeable-night and day. When I sold the amps, I talked someone into buying them both and try the bi-amping and that person fully agreed that the bi-amping made a big difference.
I forget which way the bi-amp sounded better but I do remember trying it both ways; with one amp powering the left speaker and the other the right, and with one amp powering the left and right woofers, and the other amp powering the left and right tweeters. But I do remember that while it was close there was an improvement doing it one way over the other. I think that is worth experimenting with both methods so you can find what works best.
I did not test to see if one more expensive amp would have sounded better than the two separate amps. But my guess is that while a better amp sounds a bit better than one that is half the price, I just don't see the improvement being as dramatic as what I heard from bi-amping. So I am a believer in bi-amping based on my limited tests.
I forget which way the bi-amp sounded better but I do remember trying it both ways; with one amp powering the left speaker and the other the right, and with one amp powering the left and right woofers, and the other amp powering the left and right tweeters. But I do remember that while it was close there was an improvement doing it one way over the other. I think that is worth experimenting with both methods so you can find what works best.
I did not test to see if one more expensive amp would have sounded better than the two separate amps. But my guess is that while a better amp sounds a bit better than one that is half the price, I just don't see the improvement being as dramatic as what I heard from bi-amping. So I am a believer in bi-amping based on my limited tests.