Help me spend $3000 on a used amp

I am setting aside up to $3000 for a good used stereo or mono block amps.

I have efficient speakers so the power does not have to be abundant but enough to run. The room is not big nor small so at least 100 watts plus should be efficient.

To mono block or not??? I have been debating that question.

I would like to have XLR imputs.