As mentioned cIOS249rev20b using base IOS 56 for best compatibility. Also Hermes cIOS 202/222/223/224 rev5.1 should be installed for best compatibility.
cIOS249 can be found here http://goo.gl/Y128t
Hermes cIOS can be found here http://goo.gl/Z1Pen
cIOS249 = great compatibility
Hermes cIOS = great compatibility for games requiring USB peripheral and needed for FAT32/NTFS support.