Madcat,
If you already have a payment company go to their site. They will list the carts compatable.
Usually you pick the cart with the requirements you need and find a processing company that supports it. Even cheapo carts support what you listed. One of the most important things (not on your list) is a SEO mod. Then again you can always build html static pages and link into the cart. Getting a gateway written isn't all that big a deal, if you have a decent programmer.
An el cheapo cart I like (partly because the SEO mod is only $20)...lol and does work is
http://www.candypress.com/store/scripts/default.asp
Use sql if you have a lots of products and expect a lot of simultanious users, other wise a access db is fine.
Here's an example (just to show the mod works)
-
http://www.google.com/search?hl=en&q...earch&aq=f&oq=
http://www.google.com/search?hl=en&q...earch&aq=f&oq=
http://www.google.com/search?hl=en&q...ar&btnG=Search
http://www.google.com/search?hl=en&q...ar&btnG=Search
But build a html site around your cart anyway - That was a freebie for a nice lady ...I built the html around it then purchased the $20 seo mod when she could afford it.......lol
Good luck