Thanks for all your help, everyone! I learned a lot from this thread! I ultimately did get the Eheim 2213 and got it all set up yesterday. The hard plastic piping is a little on the large side for my small tank but it all fits in there okay. The filter is just as silent as everyone said it would be, which is perfect. The flow is really good, even with a sponge over the filter intake. It's not, like, power washer jet spray or anything, which I was afraid of. It would be just right if I had fish, and the larger shrimp do fine with it, but I had to turn it down to about 1/3 the flow so the little tiny babies could still swim. (They are so tiny. So tiny!)
I think I still need to fiddle with it more to get the best balance of flow and filtration, but I am happy so far.
Thanks again for your advice, everyone!