I play with the u-boat add-on, recently I found a sound MOD by Poul. It's got sounds kinda like what you would find in the TMO super MOD. I'm not good with all the MOD stuff. But I have been using this MOD for a few days and its pretty cool. It works well for me and added many sounds to the game. I know it works with my SH4 v1.5 anyway.
It is indeed a larger DL, at about 200mb. I imagine an over-nighter with dial-up connection...I dunno, but its a great MOD.
Maybe this link will help:
http://www.subsim.com/radioroom/showthread.php?t=132995