As announced last week, Final Fantasy VI will be released on PlayStation Network as a Game Archives download on the 20th. Today, Square Enix Members overlord Shinji Hashimoto provided the specifics via Twitter.
Like FFV, which was released on April 6, FFVI will cost ¥1,200. You'll want to have 185 Megabytes free space on your Memory Stick. That's 35 Megabytes more than FFV.
Remember, this is the PlayStation version of Final Fantasy VI and not the Super Famicom original. The PlayStation version adds opening and ending CG, a bonus mode with artwork, and a run option for moving about on the fields, but it also has load times between areas.