Correct... you can easily use PowerStore without having Dreamweaver. In fact, I rarely use Dreamweaver for pre-built solutions - even when I want to modify them.
That's because the basic code and all the queries are already there... it's much easier to just open the pages in either Coda or Espresso (two incredible web code editors for the Mac) and use their corresponding CSS editors (Coda's is built in, CSS-Edit from MacRabbit is the Espresso companion).
Dreamweaver can provide a great starting point and speed up a little heavy lifting but it is much easier. in my opinion, to edit code using a real code editor.