Okay, I bit the bullet, and unchecked the "Hide products from catalog when quantity is zero" option in ProStores. Now every single card I have in my database will be displayed in a search on my store, whether I have that card in inventory or not.
Some (potential?) benefits from this:
1) This may (I won't know for a few days probably) overcome the Google search issue where if I'm out of stock my items don't show up in a Google search.
2) If I can get off my duff and price everything (which I haven't yet - I've been pricing cards as I add them - so many quantity=0 items have price=$0 as well!) then people can comparison shop.
3) People can add out of stock items to wish lists (this has been confirmed - so this one's a definite benefit - next I need to figure out how to do a "Notify me when this comes in stock" thing).
Some problems with this:
1) I still don't have photos for many items. I need to figure out what to do with them - make a "Photo Coming" image to default to?
2) If you search with the hope of buying, there's now a LOT more cards to sift through - this may annoy many potential buyers. (I'm working on creating a "only display in stock items" option in the Advanced Search, but so far the programming has proven beyond me.)
These problems, hopefully, can be overcome. We shall see.
In the meantime, if you'd like to be amused, check out the search results if you search for items in the Beta Edition (the one I have the least products in stock for).