Hi Bob,
great to read you got the Ultra 5's - they really do work don't they. It's a product you gotta have.
Make sure you have a approx. 3/8" space between the bottom of your speakers and Ulta 5's.
I'm sure what you wrote; "My bass, slam and sound stage have all improved nicely" most defiantly due from adding them :)
Granite Audio Ground Zero product - I have a very faint ear up close to the speaker hiss but only on vinyl and have not yet found the culprit - Are you saying you also had a tube hiss and by using this eliminated this. Like you ear right up to the speaker and turn up the volume and nothing?
Is this a direct sale product? actual cost? You can PM me or send me a direct email if you wish. Appreciated