As someone who is both an organ nerd and... I'll say very religiously conservative (although that's only relevant to some points), a couple things people in this thread might find interesting:

- If you're looking for pipe organs and are in the US, check out https://pipeorgandatabase.org/ . It's very comprehensive, has stoplists for most organs, and has pictures for many of the larger ones.

- I see quite a few people calling organ music boring, particularly in association with church music, and I'd like to challenge that assumption. Off the top of my head, a handful of things that come to mind:

(1) Hymns are meant to be sung with, usually by people who are not trained singers. That leads to significant limitations for the accompaniment. That said, there is a lot more variation in preludes, postludes, etc.

(2) Organ is hard. Being able to play boring hymns well with a week or two of preparation can easily take 2-3 years of daily practice, even with previous background on piano.

(3) Many recordings fail to capture the full magnitude of organ music. To repeat something that I think is a bit oversaid, but is accurate nonetheless: the building is the instrument. The building is the instrument.

(4) One thing that it's hard for me to tell is how much of the difference of opinion is that I have unusual tastes in music, and how much is that a lot of people haven't had the opportunity to hear good organ music played by a good organist.

(5) Yes, you can be expressive on organ. Yes, it's hard. Depending on the song (and the composition itself plays a big role here - don't think that a composer can't be expressive) that may come across in rubato, opening/closing the swell box (and potentially others), articulation, manual changes, etc. (I've heard just a few pieces with people one foot on the swell pedal for most of the song. They were very impressive, although I suppose a lot of that comes from the perspective of an organist. It's also very hard. See point 2.) Also:

(6) Choosing registration in and of itself is kind of an art (and a lot of fun, especially on big organs). There are so many different timbres you can get on an organ that it's really beyond comparison to most other instruments; using this alone it's easy to express everything from mournful to bombastic fanfare.

That became more of a jumbled mess than I intended, but hopefully there's something of interest to some of you.