Hi,
In my experience isolation platforms/ equipment racks can make a big difference to a system's performance. However, there are significant differences in performance between those available on the market. As a rule platforms made from heavier materals (Marble, etc) tend to empasise sonic stability and bass power (often at the expense of agility and sparkle) and thise made from lighter materials, such as Torlyte - tend to go the opposite way. Depending on design some isolation platforms will also emphasise certain frequencies so sounding punchier or more exciting.