As noted above, the maximum Shimano speced cog is 27T but Shimano is pretty conservative with specifications their so going to 30T may work but there is no guarantee it will. You will probably have to adjust the "B-screw" to clear the largest cog and are likely to need to add a few chain links if going from a 23T largest cog.
Also, any Shimano or Shimano compatible 9-speed cassette will work. Shimano Dura Ace, Ultegra, 105, Tiagra, and SRAM 9-speed will all be fine