This is a guide for u to do acoustics modding..
U can always replace the one u wanted to change.. No need to change all..
Normally, I only change the phf files only cos my farfield is perfect already for C702.. If use others, sound not good..
For eaphones, as I am using HPM-70, so modding it using Walkman-modded acoustics drivers is a plus for me 
As for flash menus, it is super easy also..
Just get respective flash menus for ur phone type, (walkman for walkman, c for c, makesure icon gps got or not also)
then u can edit the XML of any theme u like to pair with the flash menus...
after that rename that theme to other name so that u wont replace it with the old one (unedited XML)
then start a2uploader and put ur flash menus inside flash directory
tpa/preset/settitngs/system/dektop/flash
if i not mistaken la... i type spontan only..

here u go,
editing xml isnt that hard, just rename the flash menu to desired .swf accordingly

http://www.se-stuff.net/help/flash-menu.html

lol.. even the one already sync also need to use a2uploader to insert the flash menus inside ur phone..
it wont be inserted automatically along with the theme.

then u need to find original theme with flash menus of other models lah...
google it