i want to install a paypal integrated plugin on my site that does the following: 1. offer seamless checkout so that the customer doesn't have to exit the site when making a purchase 2. offers a way to provide bulk discounts if a customer orders more than X units, so the price drops from Y to Z 3. offer coupon codes functionality any suggestions on which plugin is better and will accomplish these goals??? please advise. thanks in advance.
Try s2member, a review here: http://www.flamescorpion.com/2010/05/can-you-achieve-great-things-with-wordpress/
Have a look at http://shopplugin.net/features/ and http://quirm.net/wiki/eshop/. I think they offer what you're looking for.