The Austin Museum of Art has unveiled plans for a new, three-story museum, one that’s likely to be dwarfed by the new 30-story office tower going up next door. The museum has owned the block downtown at 4th and Guadalupe for years and just sold half of it to the Houston developer who will build the office tower. The budget for the Pelli Clark Pelli-designed museum space will be $23 million, and it’ll be a block away from Ballet Austin’s new headquarters, the Butler Dance Education Center, set to open in September.