Wootheme released a Strip plugin, which integrates the Stripe payment gateway: http://www.woothemes.com/products/stripe/.
Also, if you are using ThemeForest for a theme, be absolutely sure you purchase themes from only highly rated developers/teams, because many times the developers who build and sell on ThemeForest either abandon the project if they don't get enough sales or their code sucks and your site will be security compromised, will be slow or have other problems and the developers are selling these as one offs, so they're not a company that is going to give you support. ThemeForest is literally the Android marketplace for WordPress themes and other themes and plugins for other CMS software. ThemeForest does not warranty the software and you have no recourse.
In terms of SaaS, I can't imagine how a theme would replicate the functionality of your SaaS offering, unless it has built in custom post type generator for you to manage your post types and set up a data structure.
WordPress is inherently a blog publishing platform that has since graduated to a full CMS, but out of the box, you need to customize it to take payments with the woocommerce plugin and then adopt stripe and everything. Not sure what your intent is, but generally speaking, an out of the box SaaS template wouldn't necessarily speak to your business model, whatever that is.