The Magnum and 300 were the original LX cars (sold in 2004 as 2005 models - out a model year ahead of the Charger).
I guess no one thought that a forum on luxury Chryslers would attract enthusiasts, hence the Magnum focus and dodgemagnum.net name. When the Charger hit, the name was changed to lxforums.com and incorporated all LX vehicles.
lxforums was expanded to include baby brother LC platform Challenger when it came out.
And even more recently it was expanded to include cousin WK (and WK2) platform Jeep Grand Cherokee.