As per the previous poster, what ecommerce package are you using at present?
I run virtuemart (Joomla) and this has a review/testimonial facility but I have it turned off at present because its on for all products regardless of if a review is present for a product.
Other ecommerce packages have the same functionality
I dont think dynamic will mind me saying, hes using his own custom cart. Im currently looking around for some ready made code. But its more than likely that you should make your own code if you made your own site?
Yep its custom as in designed and programmed blah blah!
Im currently looking at what amazon are doing! Im not sure to get rid of the left hand navigation altogether once viewing a specific product in order to make more room.