Another alternative: I received an email today saying CoffeeCup will be releasing its responsive Site Designer later this month. I use their Responsive Layout Maker to create wireframes and I think this is why I got the email. The workflow will ideally use both apps: RLM to design and wireframe the site; this is imported as the 'template' for Site Designer to add the design elements. Holding off on MACAW until I see this in action.