Which video cards can play World of Warcraft in the best resolution and how many GB RAMs and how good processer is needed to use it completely lagg-free

i have a new high- tech computer, same as my brother and both our computers still lag. there isn't (yet) really a way to meet requirments, an easy way to get less lag though is to ppick a server that doesnt have a high or full population. the best is to pick the new player servers.