What shopping cart/platform can I use for unlimited users posting unlimited products?

I’ve been working with x-cart much lately, and I was thinking about using it for a much larger site, but I don’t know if it can handle what I’m looking for. I need a platform or strategy that can allow for as many users as possible where each can post multiple products (hopeful up to a hundred, but that’s less important), but in their own private catalogs. So what am I looking for? With x-cart, I’m used to customizing it with jquery, smarty, and php, so I can handle that much. Can I extend an existing shopping cart, or is there one that fits my needs?

Did you check with Magento and PrestaShop. Both faciitates for many users and products.

There are many shopping carts available now a days but, you can go for some of the best like Magento, X-cart, Zen cart, Volusion, Amazon these are some of the best carts for unlimited product postings.

We have X-cart running over 500,000 products on some of them with many thousand users, categories, etc. It can handle it. What you have to look for though with any ecommerce platform is if the server running it is appropriately sized. It really doesn’t matter what platform, they all need a larger server the more resources you ask of it.