How much cayenne powder contributes the same spiciness as one minced habanero?
Notwithstanding the two current answers - that it's really hard to guess - there's an additional concern.

In terms of actual flavour rather than simple heat, you can taste (&amp; smell) habanero in pretty much anything, even at low concentrations. It's a fabulous aromatic.  Cayenne, on the other hand, is really almost flavourless in comparison.

So, as well as re-balancing your heat, you need to work on how much of that habanero flavour you want in the final product.

I'd start by dropping your entire chilli content to just one or two habaneros, no cayenne. Taste halfway through the simmer. You can add more of either habanero or cayenne at any time, the flavour of chilli doesn't really change too much over the cooking time that you can't just slip a bit more in if it's too mild.
Work towards 'just enough habanero flavour' &amp; if it's too mild, work in some cayenne nearer the end.