Greetings Scot
Welcome to Tuneland!
On your question about the Ikea bookcases, Sonic has a similar experience that might be useful.
I had large bookcases across the rear of my room against the wall (behind the listener). My bookcases did not reach all the way up to the ceiling either. I had some 4 feet above my bookcases. Bookcases, especially when filled are not diffusers. They have a strong deadening effect and if the rear of your room has echoes and excessive resonances, the bookcases should tame them. You might sacrifice a little rear ambience but that could be worth the trade at an initial stage of tuning till other aspects of your room are brought under control. The space above your bookcases of 2.5 ft is not likely to be an issue if the wall is flat and there are no windows or openings.
Just treat the upper rear corners with Corner Tunes along with the two front upper corners and you'll notice a change for the better (remember to always use Corner Tunes with the reflective side facing out into your room -- tap the Corner Tunes on both sides with your fingers and you'll instantly know which are the reflective sides).
You might want to post a diagram of how your room and where your equipment is placed, list the gear you use and what materials your floor, walls and ceiling are made of. This will give Michael and friends at the Tune more ideas on how to get your system and room sounding better. The RoomTune mini pack is a safe way to start your journey.
Sonic
Hi Scot
Good job posting your room diagram. It helps the discussion so much! You got gear that Sonic has heard great musick from -- the Naim amps in particular and the Thorens (what cartridge do you use?)
A couple of suggestions if Sonic may -- maybe it is better to leave the bookcases out of your room for now.
a. Sit between 18" to 24" from the wall
b. Move your equipment rack to the front wall between your speaker, place it close to the wall for starters. A rack in the front space will help anchor your soundstage and with the extra cable length freed up, you have more flexibility to move your speakers about. In this respect, mini monitors are fun. You can push them around easily to try our different placements.
c. Try your speakers at the front wall (back panel within 12 to 20 inches) and inner edges 4 ft apart. Toe the speakers in just a bit. Of course move them around till your get a setting you think better/best. Trust your ears.
d. Try your speakers placed just behind or ahead of the door around the halfway point, separate the speakers till they are near the edges of your field of vision and toe them in slightly.
In Sonic's experience, a system that is untuned/just at the doorstep of the Tune will give a better instant result with c. When I was starting out, d. was a no go for me. I got 3 blobs of sound -- one pasted on each speaker and one blob somewhere at the rack. The soundstage was banana shaped -- voices in pop recordings were at the front wall,insturments closer to the listener than the vocalists. Unlike live music for sure.
However with tuning, d. can potentially release losts of imaging and you can have a band lined up at your front wall with not a sound coming from the speakers themselves. (Sonic had trouble believing this was possible when I started but there is this soundtage in my listening room today...)
e. Are your Target speaker stands filled with anything?
f. You do listen with the grille cloths off the Paradigms?
Try c. and d. listen for a couple of hours, relax take some notes -- listen for naturalness in voices, bass firmness, midrange clarity, treble extension, see if you can hear a natural ambeince -- then decide on which set up is at this stage closer to the "music in your moind/heart" to use as a starting point.
g. Try to avoid having your speakers at the 1/3 points of your room width and length. You'll lose efficiency at these spots even if the frequency response may be under some conditions measure smoother.
Have fun and post your findings.
Sonic