I'm a woman with an ordered, analytical (typically male) brain, so take this for what you will.
I can see the need for better organization, but I agree that too many forums may cause guests to say "Too complicated, forget it"
I'll leave the manufacturer section alone since I saw that you just want to set that part aside for right now. How about something like this? The bold parts signify major sections like we have "Safety" and "General" ie upstairs and downstairs. Safety and Admin would be the only forums available to guests and then members would have access to some of the community forums (carseat chat, coupons, sponsors, strollers)
Safety
General Car Seat Questions – Visitors Start Here (category only)
-General Carseat Help and What Seat Should I Buy?
Carseat Safety Topics (category only)
-Installation and Technical Issues *Sticky – Vehicle Compatability
-Special Needs
-Canadian and International Topics
Vehicle and Transportation Safety (category only)
-Auto Safety
-School Buses and Other Transportation
Carseat Reviews and Recalls (category Only)
-Recalls (Child Restraints, Vehicles, and Other Products)
-Carseat Reviews
-Vehicle Reviews
News, Media and Child Passenger Safety Articles (category only)
-CPS News, Press Releases and Media Coverage
-Member Articles and FAQs on Child Passenger Safety
Community
Shopping for Car Seats, Strollers, and Gear (category only)
-Carseat Coupons, Codes and Deals
-Strollers, Travel Systems and Other Baby Gear
-Carseat Swap
-Swap O Rama
-Please Support Our Sponsors
---Sponsor SubForums
Community Chat (category only)
-Carseat Chat (On-Topic)
-Community Member Coffee Break (Off-Topic)
---Pregnancy and TTC
---Medical Issues and TMI
---Senior Community Members Chat
-Technical Professionals
Administrative
Forum Issues (category only)
-Announcements, Guidelines, Feedback
-Test Forum