296437 PayPal checkout page

I need a shopping cart of sorts..... I have several products that are sold on a website and I need an option for checking out. For example: Someone buys 1-4 quantity of Item #1, the price is $10. If they buy 5-10 of Item #1, the price drops to $8. And then directs them to the PayPal payment page OR the PaySystems payment page, depending on what they selected as their payment choice. This can be done using drop down boxes. It would be great if it had an admin interface! It needs to be able to use PayPal AND PaySystems! If you have a script already, please privide me with some type of visual on it so I can see if it is what I need!