Amarok 2
I know the OP has been told about Songbird, but I'm surprised (enough to create a new account here) that no one has mentioned the impending release of
Amarok 2 on OS X.
I'd used
Amarok 1.x about 2 years ago for a brief period and was very impressed. From the link you'll see they mention an OS X native release sometime between KDE 4.1 and 4.2. Well, 4.1 was released a few weeks ago, so it can't be long now until Amarok 2 is released as well.
If you are so inclined, you can download,
compile, and build the most recent Amarok source code on you Mac. I hope this reminder is not needed - be very careful with so much music at stake. The opening line of the wiki page should serve as a reminder as well...
...you should only attempt this, if you are truly: HAAAAAAAARDCoooOOOOoooore
I'm a daily Mac user. However, I too was looking for an alternative to iTunes. iTunes, like other Apple products, limits what the user can and can't do. I am a power user, but iTunes isn't necessarily geared towards one. Simpler interfaces make for better user experience, greater stability (and reduce the divide in the '80/20 rule' - relevant to the OP). I don't care to start a flame war, so try to look at it objectively and see that this is not necessarily a bad thing. It's a design philosophy, one that has worked well for them across multiple products and platforms.
I've experienced the same problem as the OP previously. I basically had to re-edit the ID3 tags for those albums to get things to work smoothly and there are still occasional instances where things behave oddly.
Editing within iTunes is painful. I did much of my editing on Windows before moving my music to iTunes - and I still don't use it exclusively.