The speakers are not the problem, where you have the speakers placed is the problem. No traditional bookshelf speaker is going to help you here, so stop fussing about it and save your money.
The speakers are 'up in the air' relative to your sitting position. The speakers' sound thrust misses your head completely. I have a similar situation with my Golden Ear BRXs, which I have placed on top of bookcases that are roughly 5 feet tall. Speakers sound good, but not as good as they could sound if placed lower.
Are these shelves wall mounted or part of a larger unit? If part of a larger unit, you could attach wooden shelves to the sides of the unit at about the height of your ears and place the speakers on them. Might not look pretty, but could work. If the shelves are wall mounted, can you lower a shelf?
I guess you could go with a portable bluetooth speaker like the JBL Authentic 300 and place it anywhere in the room. Won't sound as good as your Spendors though. Your Wiim Ultra should work out fine. Don't know how the Marantz would fit into this though. Hopefully some blue-toothers here can help you out.
https://www.crutchfield.com/p_109ATH300B/JBL-Authentics-300.html?tp=63340
My step daughter lives on big island. You are not kidding when you say you can't audition much.
Be well,
Rich