When building client sites that necessitate an e-commerce feature (a store or donations system for example), we use Drupal Commerce. We find it a very easy to use e-commerce portal that is fully integrated with all other aspects of the client's new website.
You need a new website because:
1) You're good looking
You built a website waaaaay back. It's still okay. Actually, it looks good. Quite good. (But not great.)
You need a new website because your business deserves to look better than your competitors'. Why? Because you are better than them. A new website says a lot about your business: it's a window into your shop; it's an advertisement of your brand; it's the first point of contact for many of your future customers.