Finding a pair of 9s is almost impossible and buying them is equal to buying a decent car. The 8b rissue probably would best be compared to a MC225 that has ben gone through as the original 8/8b was the competition for the MC225. The 5 was the competitor to the MC30 and the 5 vs 30 difference would be the same as Paul's evaluation of the pros of the 8b over the MC30 but less of the pros of the MC30 over the 8b, if any.
The 9 had no direct competing amp from Mc (mono power amp) except the MC275. The 9 made the 275 sound like a muddy, slow, detailess weakling. And the MC275 is a very good sounding amp imho. Yeah, the 9 is just that good.