Postgres case insensitive searches

Hello,
 
Grettings,
 
What is the best way of doing case insensitive searches in postgres using Like.
 
Ilike - does not use indexes
function based indexes are not as fast as required.
CITEXT - it still taking 600 ms - 1 second on a 2.2 million rows... does not use index
Collation Indexes creation with POSIX - does not really work.
GIST/GIN indexes are faster when using like, but not case insenstive.
 
Is there a better way of resolving this case insenstive searches with fast retrieval.
 
Thanks and Regards
Radha Krishna