It's probably better and more fun if you edit your own playlist to your liking, however I'd thought I'd share what has worked for me in integrating Homeworld tracks into the game. The goal here is to recreate HW's ambience, while still leaving some of Sins musical character intact. Above posts have links where you can download Homeworld music, and post #2 has a link to the tools you will need (mainly the OGG converter) to make this happen.
Here's the general strategy: songs are organized into several series in the sound file in your main Sins folder. The series are: Advent, Battle, Quiet, Sad, TEC, Trouble, Upbeat, Vasari, and the "Opening Theme". The "Quiet" and "Upbeat" series I found to be the ones most benefitted by Homeworld tracks. "TEC" could use some Homeworld replacements if you play it a lot, and I have some recommendations for the "Trouble" series as well. Naturally, don't forget to make backups. So...
Homeworld Changelog:
*"Opening Theme" replaced by "Quiet 1" from Sins (Not HW, but you'll thank me for it).
*"Quiet" Series [1,2,4,5,6,7,8,9,10,11,12] Replaced by Homeworld [1-9,22,24]
*Replaced "Upbeat" Series [1,2,3] with Homeworld [33,38,41]
This brief list removes the worst offenders. Maybe it's just me who's picky... I haven't watched TV in years and I go to more operas than movies.
Now, for the first song that it plays when you start up the game-- not the "Opening Theme," but when you actually start playing-- it seems to randomly select one of your faction peices, or from the "Upbeat" list. Advent and Masari songs haven't gotten too grating on me, not yet, but if you play mostly TEC that needs some work. Basically, for these I tried to choose the least spooky Homeworld songs, which turned out to be a difficult task...
*"TEC" [1,2,3,4] replaced with Homeworld 6,9,42,45
*"TEC Opening" replaced with Homeworld 10
*"TEC Theme" replaced with Homeworld 46
*"TEC Announcement" is fine, and for "TEC Quiet," I'll let one TEC melody stay in... for now! =p
(Alternatively, while I avoided all tracks with recognizably distinct Homeworld melodies, if this is not an issue for you, then Homeworld 11,13,14,16,20 are all options for the TEC or Vasari series, and the Adagio tracks 18,19,26,35,38 might go well with the Advent.)
The "Trouble" series [1-9] can be hit or miss, overall it's not horrible. The main reason I'd suggest changing to Homeworld is that the Sins original "Trouble" series clashes at times with the Homeworld "Quiet" series. Maybe you can wait and decide for yourself. Homeworld 15,17,21,22,23,28,32,42,44 have ominous undertones that make make good "Trouble" replacements.
The "Battle" series turns out to be pretty good, which I hadn't noticed before because I always had the music volume turned off by the time the battle started. So I'm in a mind to leave these alone--it clashes slightly with Homeworld music but not bad at all I find. It does give the game it's Babylon-5 space battles character. Personally, if I were to make changes here I'd probably rip some Puccini-- Madama Butterfly and Turandot most likely-- and heck, why not a little Wagner?
These changes make the game go from me turning the music volume down within the first five minutes, to sitting back and enjoying it, as the soundtrack blends mostly seamlessly into the gameplay.