Wil, I agree with your point about looking for someone who is passionate about search. I’d even go a little bit farther and research how active those top level managers are on LinkedIn. Are they just out there promoting their business through groups or are they answering questions and providing knowledge? Heck, you could even check out Quora.
One item that I believe helps your and Seer’s reputation that you didn’t mention is your plethora of SEO videos on Youtube. Doing some research on potential SEO companies on Youtube/Google Video search can give you an idea if the company is respected as a thought leader.