Installation of sound and insulation in a business center

Our business center decided to upgrade the sound system and add soundproofing to the conference rooms and common hall. We want to find a service that will take care of everything at once: from design to installation, so we don't have to run around to different contractors. We've had experience with individual companies that only installed the equipment and didn't think about the acoustics of the room at all, and as a result, everything sounded bad. Maybe there are proven options for a comprehensive approach?