Check out the Miva Shopping cart. It allows PayPal when you first get started, and as business picks up it allows for a real merchant account.

It will do everything you ask.

(mod edit: no self-promotion, please)
just visit Miva.com.

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For ecommerce credit card processing I operate http://www.121merchantaccount.com
For SEO and Internet Marketing I operate:
http://www.serr.biz