Best eCommerce Store Plugin for Artist Website

We have an artist portfolio type website set up with wordpress and using the “Responsive” theme. ( http:/www.studiopatrice.com ) We intend to sell canvas transfer / giclee prints from an e-store.
Our hosting company has a free e-store, call Easy Store Maker Pro, which we have been trying out(click store link on website) but the theme is different to the website and we would like to make it more professional looking.
We would like to make it easy for our visitors, browsing our website, to simply click a link on a painting’s landing page (in addition to a store tab as we have it now), if they wish to make a purchase. Easy Store Maker Pro does not do that for us. Also we would like the theme on the store to be the same as the website.
We would like keep the website looking as it is, like an artist portfolio. But the moment a vistor clicks a link to the store, they are treansfered to an artist ecommerce site. When they click on a “landing page” link, they are taken to the e-store page to puchase a print of that image. When they click on the “Store” tab, they are taken to the “home” page of the ecommerce site to view the prints that are available for sale.
Does anyone know of a plugin that can do that? Would I or Should I change the theme from “Responsive”?