I recommed these. Wordpress with ecommerce module. Wordpress great as a CMS with seo friendly urls and pages and also if you add ecommerce its great to have. Oscommerce with SEO Urls integrated and many other mods available as contributions choose the right modules as per your requirement, some mods require php/mysql technical knowledge for integration, but you get a lot of low cost support. I recommend going with older MS2.2 version. Magneto is also good with many features.
I would vote for zen-cart if comparing OSC with ZC. Generally speaking, any E-commerce scripts using template systems would be easily for customizing purpose. Thanks,
It depends on what you are looking for. If the look/design is not an issue and you want rich features and good online community, Zen cart should do the trick. Not the easiest cart to skin, still easier than OS Commerce. And by skinning, I mean to actually make it look like your own site, rather than another template. Magento would be a great choice too. There are literally hundreds of carts available, both commercial and free. Make sure, the one you choose has the features you need, including support for the payment gateway of your choice.
Well dear in your situation you must try "Magento eCommerce" its totally free of cast no hidden charges.. must try that..