I've always been advised ( a number of times from lots of shops and people) that spending the same money on an integrated amp is better than spending the same money split between a cheaper integrated and a power amp. Paying for extra power supplies, cases, packaging etc. Note I'm not talking about pre/power combos here.
However if you already own an integrated then adding a matching power amp can be a good upgrade.
I'll just get my fireproof jacket and wait for the protestations