Thank you both for the comments. I really do like the appearance of the Quadraspire Sunoko Vent rack, but decided to postpone that purchase until after trying a few isolation tweaks and maybe an audiophile fuse. This seems the most sensible upgrade path for better sound. I do have an open mind about audio tweaks but have little experience in this area. My system has gone thru a lot of changes in the past two years and is now pretty well sorted with Lumin, Belles Audio, Harbeth, and Triode Wire Labs cabling. So now may be a good time to try a few tweaks. My first try at this last week has yielded some great results!
Before buying a vibration accessory, I experimented with placing a book on my streamer/dac and integrated amplifier and listening for any change in the music. The most notable change occurred with the Belles Aria integrated amplifier. After doing some research on damping products, I ordered Harmonic Resolution Systems (HRS) Damping Plate (DP II $235) from Paragon Sight & Sound. The results with the damping plate were even better than expected, with improved soundstage, depth, and clearer, more powerful bass response. Needless to say, I ordered a second plate for the streamer/dac yesterday.