Price Comparison Site

I'm looking for some kind of comparision script. It needs to have a menu to select products from, then once thats selected it goes to a “category page” where it compares products with prices. Then after selecting product it goes to a “product page” where you can see picture and all shop prices of this product. The best way for communication in my opinion is create php script, which allow generate XML file with prices from shops. Note: I don't want to compare products against each other, just i want to compare prices of a product and other info with it. Thanks, Adrian