Customizability of Powerstore

I have a potential client who wants an all in one online store, including a CMS, so Powerstore looks perfect. Before I go buying it though, I need to know some things.

How much of the front end is customizable right out of the box? Can I completely redesign it or integrate it into an existing site?

Basically, I want to be able to make it look like they want (which is completely different than the standard design on the Demo page), and have the full CMS that comes with it. I'll likely be buying the Powerstore 'solution' as well as the Super Suite for all the other great things it has. Is there a tutorial somewhere or description on how to integrate the Powerstore or modify it?

My other option is Cartweaver, which is about the same price as Powerstore, has a CMS and can be integrated into an existing design. Cartweaver looks dated, but again, it's fully customizable and can be put into an existing site...

Any help would be appreciated as I plan to purchase something in the next couple days if the customer accepts my proposal.