an interesting thread. as others have posted. Bi-amping has a lot of plus and minus and it all depends on what you are targeting to solve or improve.
for me, I had the weird idea of biamping the ATC speakers. what I did was to use the X150 to drive the mains and XA25 to drive the tweeters,
I personally did not find a major improvement, there was some change, I would like to point out a better dynamic, but not enough to justify the extra cost of an amp.
YMMV though ..