A high quality rack can make a difference in bass extension and impact, soundstage width, imaging precision, treble purity, upper bass bloat, etc. Unfortunately, like cables there is a lot a mumbo jumbo fast talk about what constitutes a good rack design. Some of the most effective racks have radically different designs and it is virtually impossible to really compare one design with another. In addition to the brands you've mentioned I would suggest you check out Gran Prix, Pagode, Solid Steel, Mapleshade and Sistrum.
