I think seperating sub-models of each "brand" would be more beneficial. Some of the sub-models of the same brand are more different than TT vs. 5er. Also as far as navigating the site, no its not hard if you belong to one forum you should be able to generally navigate most. Newbies will not search and continue to ask questions that have been answered no matter how the information is organized.
2012 Flagstaff Micro-Lite 23fb
2010 Toyota Tundra 4.6l V8, 4x4, tow pkg, 4:10 gears
2013: 12 booked so far