Powerstore VS eCart

I need to add a store to my existing site which would make me lean towards eCart verses PowerStore for 2 reasons:
1. I already have a site design
2. eCart has been updated more recently than powerstore

Reasons I would prefer powerstore would be the features that are already included:
!. Order History, Update with shipping confirmation with automated email, log in, users, add product... basically everything you need is already done and per our conversation you can easily update the theme to a custom theme. So then why would you want all the efforts required to create all these backend features.

Option 1 install Powerstore on my site in a directory store, and add the theme of my website to powerstore and use Powerstore for all shopping functions
Option 2 - Use eCart and Datassist for all products and obviously use existing theme.

Can you easily use the Powerstore Database with Datassist for custom pages?
Another question - Can you simply use Powerstore for the back end and DataAssist to show the products and somehow use the two together.