This help page covers the matter of cart customization, if you can get the overlay-style cart that appears "inside" the seller's page:
http://www.e-junkie.com/ej/help.custom-cart.htm
However, I don't think those techniques can work with a Wix site, since I don't think Wix will let you edit the raw HTML source code of the page where their Flash animations are embedded, and thus you may not be able to implement the overlay-style cart inside your pages there.
The trouble with Wix in particular is that it's a proprietary site generator service that builds sites as interactive Flash animations, rather than the more typical HTML-based Web pages that E-junkie is designed to work with. Even for experienced Flash/ActionScript developers who build Flash-based sites completely from scratch (rather than using a service like Wix to help generate the site), using E-junkie in a Flash-based site can be challenging:
http://www.e-junkie.com/ej/help.flash-shopping-cart.htm
Products using Variants/Variations are even more challenging, because the button codes we provide for those products uses an HTML form, rather than a simple linked button. You might be able to manage adapting the form-based menus into a series of buttons, as explained in this tutorial:
http://www.e-junkie.com/ej/tips.variants.button-tutorial.htm
In the case of a Wix site, once you derive the URL for each button, you'd just use those with whatever link/button maker widget Wix provides in their site generator interface.
