I would say the World Fitness Convention is the best place to shop for equipment (http://www.ideafit.com/conference/idea-world-fitness-convention-2011). If you are not planning to attend any sessions and want to purchase equipment only then contact IDEA and they’ll give you a free expo hall pass.
I shopped around everywhere and found good deals on Craig’s list and ebay but, some of the more costly items I purchased from (http://fitnessblowout.com/). They don’t have knowledgable professionals or great customer service but if you keep an eye out for deals, they certainly do have those. (ex. free shipping, upgraded free lifetime warranties, etc.)
Idea fitness convention in LA of course! Fitness wholesale (www.fwonline.com) & stott Pilates for any Pilates equipment, hands down the best quality.