You may want to try setting up DMZ mode or port forwarding.(28910, 29900, 29901, 29920, 80, and 443.) More help perhaps in here:
http://www.shoryuken.com/showthread.php?t=223443
I am using wireless and only have like half a second of input delay at most ever. Most matches are playable for me, though jittery every now and then.