There's a few active threads that will give you a good idea of what to look for

http://www.dual-boxing.com/showthread.php?t=42416
http://www.dual-boxing.com/showthread.php?t=44292
http://www.dual-boxing.com/showthread.php?t=44243
http://www.dual-boxing.com/showthread.php?t=43179

Start going through them and once you have a few ideas, bring up those so you can get specific answers.