OP here. Thanks again for all of the sage advice! I am definitely out of my league here in terms of budget and experience, but it’s good to get advice from those who know a lot more than me. I need to go through all of this information in detail once I have a couple of hours free. Just some general comments:
1) The bookshelf on which the speakers are placed is an open Etagere style bookshelf with an open back, so there is approximately 10" of space between the back of the speaker and the wall. Still not ideal, but maybe not as bad as an enclosed bookshelf with the speaker pushed up against the back panel.
2) The Jamo 803s which I currently have on the bookshelf are front ported, and perhaps that is why I feel that the Jamos sound great for what I paid for them (around $130 for the pair). But if I narrow down my choices to front or side-ported speakers that would fit within the bookshelf space (less than 14-1/2" height) I have much smaller category of choices. Elacs are often front-ported, but most won’t meet the height requirement. Perhaps the Golden Ear BRX would be a good choice? I haven’t seen that mentioned by anyone. The LS50s would fit in that space, but are rear-ported. I think I would likely get stands if I ended up getting the LS50s, however. Many of the speakers on my shortlist are too tall. The Klipsch 600Ms are too tall. And the Monitor Audio Silver 100s are 1/4" too tall. The Polk R200s would fit but are rear-ported.
3) I do have a subwoofer (Polk PSW111).