Has anyone experimented with switching the Havana

Yes, it is not the chip model that changes. It is the grade of the same chip. The ones in mine originally were "L" grade. They can be bettered by the "J" grade and the best is the "K" grade. They are the same chip but when they are made they are tested and sorted by performance.

I did mine as well. It was a really solid improvement. Gives a better sense of resolution and just a better overall soundstage. For sure it would be one of those things that you don't notice until you do it, and then you can't go back after you do.

It was not hard to pull the old chips out and replace them with the new ones, either.