Thank you all for excellent advice. I will lose the mat, even though it definitely helped with the Music Hall. Also, a maple cutting board from Michigan Maple and Isoblocks from Mapleshade are on their way to help offset my iron and glass rack's poor isolation properties.
As far the phono stage, my Rotel doesn't have one, so the Soundsmith is the only one I have on hand right now. However, I'd think that it should be a good match for a Soundsmith cart, shouldn't it? The capacitive load of the cart is equal to the input load of the preamp at 100 pF plus the cables will add more, but it's my understanding that this should not be a problem unlike when the cart has a higher capacitive load (e.g., 400 pf) than the preamp. In fact, Soundsmith considers carts with 100 and 200 pf, virtually the same. Admittedly, I am rather a novice to analog and my understanding of much of the terminology is still quite basic. Please feel free to educate me if appropriate here, or perhaps point me into the right direction.
Finally, I'd like to make sure that the VTA is set properly, or at least that I know what I'm doing. From the description on musicdirect of the JMW-9T, this upgraded version of the JMW-9 Standard has "a low friction bearing mounted on a solid stainless steel rod with markings to set VTA (Vertical Tracking Angle)." The manual makes no mention of it and I'm not sure what to be looking for. Do they simply mean the threads on the shaft of the rod as you move it up or down? This could hardly be used for precise adjustment. Would getting a test LPs help dial things in? Some of the descriptions of the test LPs sound kind of intimidating to me. And they're expensive!
Again, I sincerely appreciate your input and advice. This forum is indeed an invaluable resource to us all.