You can improve your brand detection parsing the last 6 digits (normally) in the user agent (before plugins).
In this website there is a very nice catalog: Unknown User agent fragments
“Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; WOW64; Trident/6.0; Touch; MAARJS)” --> Acer
“Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0; Touch; MASMJS)” --> Samsung
I can contribute sending hundred thousand of user agents from different countries if you need it for general testing