I personally love strong rythms in the background music.

Just like the sequences Jerry Goldsmith used for the Romulans and which are also in your compilation for FO. (Tshk-tk-tshk-tk-thsk-tk-tshktk-tshk-tk...)

Or for example the "Pirates" theme from Pirates of the Carribean (heard in the title "Underwater March" and others).

As long as it sounds strong and rythmic, it is good for playing as it drives you forward. You play faster, more aggressive.

That would be very fitting to the Jem'hadar.

But don't forget the founders. There should be very fluid and organic music also, almost without percussion.

So, all in all, I think you should change between aggressiv, stomping, rythmic war music and creepy, not so loud and slow music.

That would do it, I think.