Development of highly scalable web site

Not sure if this is the right place to post this but here goes anyway.

We are looking to hire an outside firm to help with development of a scalable and potentially high-traffic web site. We are not looking for an individual but rather a firm with enough well rounded expertise to help us with various aspects of this.

Basic requirements:

LAMP stack or other open source solution
Very proficient in cross-browser web development
Flex/AIR development for RIA
Java/C/C++ proficiency
Expertise with Comet and push server technology
Experience with development of high-traffic web sites
Use of Amazon Web Services infrastructure a plus

If anyone knows of consulting firms that can take on such a project, I would appreciate your feedback.

TIA