I have my website that's basically a webstore. I've been running with Yahoo SiteBuilder and a Paypal 3 party cart. My website has about 30 pages without calculating the pages generated by the cart.
Yahoo SB has not been uprated since 2009 and anyways, I did push SB to it's limits with website. I've been using SB since 2004.
At first I was looking to use Dreamveaver but a computer artist friend to me to expect a big leaning curve compared to SB. I don,t know is this is true? Then I read here about CM like Wordpress or Durpal.
Not being familiar with Sitebuilder, can you describe your shop? Does Paypal handle all the cart functions?
If you want a regular e-commerce site with a full shopping cart on your site, this is a fairly big undertaking and I would say that unless you're up for it, it's smarter to use a fully hosted product like Business Catalyst, Big Commerce or something like that.