What are the best e-commerce modules/setups?
I have not yet built an e-commerce site on D7, so I cannot get really specific. 

That said, the obvious starting point for e-commerce on Drupal 7 is the Drupal Commerce package. Just start with the basic package, see if it fits your needs, and install add-ons if you need them. There even is a dedicated Drupal Commerce website with documentation, a forum and more.

There are a couple of themes that are specifically geared towards e-commerce, for instance Acquia Prosper and AT Commerce.