UPDATE - Well, I am pleased with the improvement we've seen so far. I've re-installed the chat box, but I made a few small changes.
The page loads quite fast, only the chatbox and the Latest Posts pane take about 5 seconds to load after page refresh.
Related: is there a way to put newest messages at the bottom rather than at the top? I could not find any post about it in the fora nor any option in the profile settings.