Ecommerce Website - Zencart or Custom

We have a need for an ecommerce website to be built for a client of ours. They are in the printing business. Basically, there are two directions to go, using an open source solution like zencart with some customizations or built a custom system. We are open to suggestions. Below are the specific requirements that may help your determination as to best solution: 1) Manage Categories and products through backend 2) Ability to use Canadian Fedex and UPS shipping modules 3) Integration with Gateway (to be determined).. probably PSIGATE 4) Taxes 5) When order is placed an email is sent to customer and seller and distributor 6) Client will be selling many products including Business Cards, Letterheads, and Envelopes. All products will be like any standard product except for these three which are unqiue products and have a unique functional requirements: When the user places an order for a business card, besides specifying a quanity, he will also specify the following: Title (drop down) Name Address Number Type (Home/Office/Fax drop down option): Phone Number Number Type (Home/Office/Fax drop down option): ) Phone Number Number Type (Home/Office/Fax drop down option): ) Phone Number Email Address He also, has the option to specify 2 side and in that scenario, the same fields above appear but in French. At any point, the user can click a preview button and they will seel a pdf or TIFF of a business card with all the fields they have inputted. The location of the fields will be static and coded into the system. Letterhead and Envelope will work in a similar fashion except different fields will be required for those and the realtime actual preview example will be of a letterhead or envelope. The purpose is to asllow the user to see what the final product will look like prior to ordering. We are open to suggestions in terms of the flow of the dynamic creation process. 7) After the user places an order, in the backend, the admin should be able to download a high res image (in PDF or Tiff) of the file generated by the system for the order. Of course an order can have multiple proofs. 8) We would like a central area in the admin screen where the admin can download all the files for all the orders at once as opposed to going into every order and downlaoding the proofs. And once all the orders are downloaded, we would have a flag or something to indicate that the files have been downloaded and then when we get back to that screen, the orders that have been downloaded would not appear. We copuld always have a flag (even order status) to indicate that as long as we can do a mass update on the order status at once. There are many ways to do this, but of course I am suggesting Order Status for those that are thinking zencart customization. 9) Optional, but preferred: Not sure if this is possible with customization in zencart, but obviously doable as a complete custom solution, but if we can create many admin accounts with limited access that can only see certain orders and they can approve those orders. Its for the dsitributor to approve orders after they confirm its in stock to ship. Please quote this separately. Items 1 to 4 and possible 5 can be done with zencart out of the box. Items 6 to 9 definitely need some customization done to zencart. The key question is whether we are better in going with a basic cart custom solution or a modified zencart. So we are open to both. WHen bidding, you need to let us know whether you propose one or the other (zencart vs. custom) and cost as well as please indicate the cost for item 9 separately. Also, quote item #2 separately if you are pursuing the custom solution route. Thanks.