Thanks to all for the thoughtful comments.
Regarding changing integrateds vs. moving to separates, my thought process has been: it will be easier to tailor the sound by investing in a quality pre with the potential for playing nicely with a variety of power amps. Perhaps one with variable gain and a low output impedance. Swapping integrateds with more power is attractive because it does reduce complexity and may play cleaner at higher volume, but it means losing flexibility and is at the risk of not sounding as good as my current integrated.
Fun to think about though...