Actually, most if not all Marantz gear have have collars that prevent spades from being used. Another reason why I love Marantz
I have the bluejeans locking bananas on my Marantz right now.
If you bought the locking ones, you need to release the lock first or they will not fit.....
ALL Marantz gear ships with the blocking caps installed in the binding posts, so these do need to be removed first as mentioned.
I've been using connectors on the ends of my wires for YEARS with no issues. Does it make the sound better or worse? Nope, but it sure is 100% easier to setup when I change things around. I did have some bananas that became loose and slipped out of the posts on the back of the receiver, which is why I only use locking plugs for those connections now.