You can also add another 9800GTX if you want a bump in performance =)
Worst FKin Idea EVER !!
Either wait for the HD5850 series to come down a bit or else get and HD4890, but adding a second GF9800GTX is plain stupid, especially heading forward.
But to the OP, did you bother checking the Champions forum first?
You're not the first person I've heard this from and low and behold there's a mega thread at the online site about the lag;http://forums.champions-online.com/showthread.php?t=35438
and some advice about rolling back the nV drivers to imrpove performance where alot of lag was introduced with the latest driver update;http://forums.champions-online.com/showpost.php?p=1251694&postcount=1184http://forums.champions-online.com/showpost.php?p=1252320&postcount=1186
So don't buy a new card, and definitely don't F'in buy another GF9, see if rolling back the drivers helps and then maybe check the thread for updates.