Can you use a Shimano RD-6400 "600" rear derailleur with a 9 speed cassette? A 12-27 cassette if that makes any difference. From what I have read, I think you can.
And can also use any 9 speed shifter-- including the ultegra and dura-ace 9 speed brifters? Again, I think the answer is yes, but I am looking for some confirmation.
What about the matching front derailleur? Will it work as well?