Best flat irons? > PLEASE ANSWER!?

okay so i have natural spiral curly hair but i alwayssssss straighten it. the straightener i have now is rom the mall :/. it works for the most part but i can never get it allll the way straight & i cant get it to stay that way throughout the whole day. i was wonderin if anybody had any suggestions about a realllyyyy good flat iron ? (PREFERABLY PROFESSIONALS) maybe a chi or solica ?? PLEASE & THANK YOU