Thanks! Next, you should back up each of the text files you listed here. Put the backups in their own folder, don't rename them. Then (and I'm assuming you have Xenophonia installed and that it's working correctly):
1. copy xidx.exe and extract_audio.txt from the Xenophonia folder to SS folder.
2. copy all the text files named export_descr_sounds* and descr_sounds* in the Xenophonia\data folder into the SS\data folder.
3. copy the entire folder named "text" in Xenophonia\data and paste it in the SS\data folder. This is needed to make subtitles work for all factions.
4. copy the entire voice folder in Xenophonia\data\sounds into SS\data\sounds.
Next, time for some overwriting.
1. Run extract_audio.bat in the SS folder. This will unpack whatever additional sounds SS has (including music).
2. Once done, back up the dat and idx files in SS\data\sounds (move them into a backup folder, don't copy, don't rename). You can leave the effect_evt folder where it is. The files can't stay where they are or there will be no changes in the game, but you might need these later in case this whole thing doesn't work.
3. Download
this file and unzip them into your SS\data folder. Overwrite all.
4. Run Stainless Steel. Make sure the shortcut has the --io.file_first switch or some factions will be missing subtitles and diplomacy messages. The game will pack for a few minutes and then reach the main menu. When it does, quit.
5. Now you should be able to play the game. Keep a backup of the file system.log.txt in your M2TW folder regardless of whether everything seemed to go well or the game crashed.
EDIT: Ok, I've done the edits some Russian units will likely be silent, but I don't have the time to make the necessary changes. Make Grand Duke can help there