Suggest us on developing comparision shopping:
To be based on core of some Shopping Cart Script like Prestashop (preferred),Magento Community Edition or as you suggest.
Able to parse XML feeds from Affilaite Marketers like Paperjam,CJ,Linkshare,Share a Sale etc. convert to database-MySQL or as per shopping cart script.
Develop a script to search these products by Brand,
Content and Mapping modifications can be done by us.
or if some ready solution is available to implement complete comparision engine, with strong control over theme and appearence send us examles through pm..