Best Shopping Cart Plugin?

Hi, there are so many plugins for e commerce and bevor I try every single one I wanted to ask if anybody can recommend one specific for my needs.
What I want is a “Add to Cart” Button which I can place in a standart wordpress post.
Very important is that I have stock quantity because I am selling limited editions.
A simple checkout out page without registration and paypal payment.
Important here is that customer have to check a box (terms of use) befor finishing checkout.

Very simple, nothing fancy.

Any Help is very appreciated.