Offline download of Enhanced Dictation in Mavericks
I had the same problem and i figure out how to solve it

I wanted to keep the file so I don't have to re-download every time

here is the way tested on mavericks 10.9.3 and it works

download the file 785 mb

when it finished go to

SYSTEM --> LIBRARY -->SPEECH Recognizers

SpeechRecognitionCoreLanguages this is the folder 

hit get info and look at the size simply copy and paste that folder and save it , if you need to install in another computer copy and paste the folder to that location , if you ever reinstall the system you don't need to re-download because you already have it

here is the link for the pkg i haven't try this pkg yet i just got you the link

http://swcdn.apple.com/content/downloads/55/13/031-1940/chpuvr2ntbhisy2em872b4j6hsk71croja/SpeechRecognitionCoreLanguage_en_US.pkg