I agree wholeheartedly with Ric about the UI Browser suggestion and in fact you can use it to start looking for attributes of those GUI items which can be used for developing your "if then thing".
I have also found that using the repeat loops instead of the delays tends to help with reducing some of the problems of transferring scripts to other computers. UI Browser was also invaluable in finding the attributes required for the repeat loops.
Here is a further development of the scripts that have already been provided. I have assumed that your two output options are on row 1 and row 2 of the list. If they are not then there are two options:
1) if they will always be found in the same location in the list then just change the row numbers in the "if then" clause;
2) if they are not always found in the same location because you have other output options which come and go then there will have to be some further checking. This is possible but I did not add it here because of the added complexity. Let me know if you need it.
click here to
open this script in your editor
<pre style="font-family: 'Monaco', 'Courier New', Courier, monospace; overflow:auto; color: #222; background: #DDD; padding: 0.2em; font-size: 10px; width:400px">tell application "System Preferences"
activate
set current pane to pane "com.apple.preference.sound"
end tell
tell application "System Events"
tell process "System Preferences"
click radio button "Output" of tab group 1 of window "Sound"
repeat until (value of radio button "Output" of tab group 1 of window "Sound") is 1
end repeat
if (selected of row 1 of table 1 of scroll area 1 of tab group 1 of window "Sound") is true then
select row 2 of table 1 of scroll area 1 of tab group 1 of window "Sound"
repeat until (selected of row 2 of table 1 of scroll area 1 of tab group 1 of window "Sound") is true
end repeat
else
select row 1 of table 1 of scroll area 1 of tab group 1 of window "Sound"
repeat until (selected of row 1 of table 1 of scroll area 1 of tab group 1 of window "Sound") is true
end repeat
end if
end tell
quit
end tell
</pre>
PowerBook 12" Mac OS X (10.4.6) 
