Shopping Cart Checkout / Backend Database Solution

We are looking for a professional backend programmer for shopping cart website. The company sells one-of-a-kind RUGS (Oriental & Persian Rug Dealer). We will be designing the frontend of the site (graphics, products, template, etc.). The site is currently hosted @ GoDaddy (Linux server) so cart programming can be done in PHP/MySQL/JavaScript. We can take care of the merchant account set-up. What shopping cart service would you recommend? (Yahoo Store, MonsterCommerce, x-cart, etc.? ... or would you do custom?) Website Database / Inventory / Shopping Cart SPECS: 1. The site needs to be able to process credit card payments for Visa, MasterCard, American Express, and Discover. 2. There is no inventory database at the store to match against, so a new database will need to be created. 3. Standard fields for the inventory database will include SKU, size, color, style, price, weave, backing, construction, place of origin, fiber. Other fields may need to be added later. 4. Customers need to be able to login and register an e-mail address with the website to store preferences and order information, and for promotional mailings to customers. 5. Initially 100 rugs will be entered into the product database ... eventually 4,000 products will be added after the new site is available. 6. Each rug for sale on the website and at the physical store is individual and unique (one-of-a-kind); so, once each rug is placed into a user's shopping cart, it cannot be displayed to other users currently viewing the site. 7. Because of this limitation, shopping carts should NOT be savable, and there needs to be an idle shopping cart time after which the cart is emptied (maybe like 5 minutes). 8. An appropriate warning should be given to the user regarding shopping cart limitations. 9. The website should suggest other rugs to customers based on characteristics (size, color, style, etc.) of the current items selected for purchase. 10. The website needs a search function to allow searching on common fields. Please PM me for ideas/comments and answers to the above. I can also show you the current site and send you URL.