Ok, so the first thing I realize when I visited your site is that you are an SMC retailer ... not a problem ... just an observation.
Secondly, do you carry, or are planning on carrying any other vendors besides SMC?
Thirdly, why are you only looking at Cart solutions that host your data base, cart solution, and web site?
Would it not be wiser to find a cart that provides a solution that allows you to grow and have your site site custom designed ... rather than a cookie cutter site?
There is a great new cart available ... very affordable ... and is proven to place you well in the search engines for virtually no SEO (search engine optimization) costs at all.
Check out the cart and the design at this site ... Click Here ... at see if this is something that you want your site to look like.
The cart offers drop shipping, gift certificates, unlimited categories and sub-categories (all user defined), multiple quantity discounts, defined discount codes, multiple shipping charges options, selected products -FREE Shipping, banner ads program, and a very proprietary program that will drive your site to the top of the search engines (proven by a number of web sites, including the one that you will visit).
And best of all, the cart and data base is fully developed ... and proven. No need for your designer to have to write complicated code (of which the designers using ZenCart and OSCommerce like because they can charge you big bucks for "their" customization.) ... the modules are already there, to be turned on or off.
And it integrates easily with a wide variety of Gateways, including Authorize.net, PayPal and others.