I think XFORCE and DC is the same thing... (well one is copied off the other... can't remember someone will have to correct me *cough fred*
Don't know too much about USDM headers haha but I can tell you this...
At that price... get the Weapon R Header...
It is an amazing header and beautiful haha mine is like blue now :P
The Weapon R design and air flow is really good and provides more gain compared to the other Top Speed Headers...
Top Speed Headers
http://i.imgur.com/yZEET.jpg
WEAPON R HEADERS
I would imagine XFORCE, DC AND TOPSPEED will be quite similar since I think they are more USDM design whereas the Weapon R is more JDM despite it being an American company...
blahh last sentence was more of a guess so don't take it as factual.. just trying to help :P