Here's what I came up with.
Two 23x23x10 GIK full-range Sound Blocks on the floor behind the speakers. Big improvement.
Removable/temporary items:
Custom made black quilted cover for TV from Digital Deck Covers. Doesn't look terrible and it is quick and easy to add/remove. Makes a big difference on it's own.
"Velvet" curtains for the china cabinet, window and french doors on same wall as system.
Treating the main reflective surfaces really improves imaging - specifically spatial accuracy / separation of instruments/vocals.
$600 all in. The removeable stuff takes 5 minutes to set up.
John at GIK was very helpful and did not try "over-sell" me.
Thanks for the advice.