OP, do you have sloping roofs on both sides? And do you have two walls or one open wall on your 18ft?
If yes, your room is very similar to mine (which is upstairs, have a look into my virtual system). In this case, both floor stands and bookshelf speakers could work nicely for you. They do with me. I am sitting as well near the end of the 18ft side, open wall in my back.
What I had to do when moving in with my gear was concentrating on the placement of the loudspeakers, including some room treatment (using wooden crates for the vinyl records). I found out that sitting not too far from the large front speakers (about 6ft) is the ideal position for me. Especially small Jazz groups and femal voices sound very very nice to me in this room.
Sometimes, I am also listening to music using the bookshelf speakers being part of the HT system as surround speakers. Adding the sub, I had a great sound experience just a couple of weeks ago when ’tweaking around’ with my sitting position.
I can imagine that both kind of loudspeakers will work for you as well. BDW, your Olympica 1 should not be the weak part of your system if your room has a sloping roof.
Best, eagledriver