If have that kind of presence, bound to gain aggregate value for organic listings because, if marketing well, traffic will go up, click-through rate will go up and conversion rate will go up. Firmly believe that if improving those things rankings will improve also.
That being said, PPC, if it's really well done, can augment results and could possibly have a residual effect that does benefit SEO
One other consideration is that any advertising do, whether it's PPC or print or radio or TV ads, it augments Direct traffic. Direct traffic is the golden ticket. Anyone directly typing URL into their search bar is already friend of the concerned website. If can increase direct traffic pool via PPC, then it's worth every penny.
The other positive aspect of running PPC ads is that it increases exposure (both search and display), and leads to a rise in branded searches. Branded searches, like direct traffic, often convert pretty nicely, and help to send more signals to Google that the proposed website is a brand and should the lovely treatment they often provide to brands. There are outstanding benefits to ppc advertising for SEO.