You really can't go wrong with Wordpress/WooCommerce combination. I'm not really big fan of that particular theme that they are using, but I highly recommend searching through woothemes. I've been developing websites for 15 years. In my work-life, I am a full-time web developer for an ad agency and we are the agency on record for 2 of the top 10 brands in the world. This is to say that I always use Wordpress for small to medium businesses websites and recommend Woothemes to anyone trying to DIY it.
If you don't want to go the Wordpress route, then you can also consider Magento. The community edition is free and open source. There is a lot of big-time companies that are using Magento today.