I immediately thought of George Lucas' THX, which is a very strong, recognizable brand name. THX could easily claim your domain name is confusingly similar to its TM and therefore infringes on the TM.
THX the sound company comes from the Movie THX 138. But to me it will always be the license plate on John Milner's deuce coupe in american graffiti "THX-138'' To me is a little or no value name