No need, I've got an answer for you. I'll give you all the instances I know of.
Track 1 - Obviously the intro theme
Track 2 - The first part is used in Episode 7 when X-Bomber comes out of the Black Hole and the latter part of it used a few other time (but I don't think it had the drum beats). The second part is used quite a few times basically a threatening sounding Alliance theme, also first used in Episode 7. The ending part I don't recall being used.
Track 3 - First used in Episode 9. This is The Imperial Masters theme.
Track 4 - First used in Episode 18, and at the end of Episode 21 (Episode 20 - UK). It was also used in the "X-Bomber" Preview show during the Imperial attack on Pluto Alpha Base, though was not used in the final Episode.
Track 5 - Used quite a few times.
Track 6 - Never used, which is a shame because it's an awesome theme
Track 7 - Another gloomy theme used a lot on the series, usually at the beginning or end of an episode.
Track 8 - Used a couple of times. The main time that comes to mind is when the Dai-X fighters launch from X-Bomber on Pluto on Episode 5
Track 9 - The Beginning Part was never used in the series, but the second part was used. It is used the first time we see Lamia, and is pretty much used as her main theme.
Track 10 - Was never used.
Track 11 - The Astro fighter Theme. Used as The Pluto Astro fighters are launched from Pluto Base to be blown up by Makara's cruiser.
Track 12 - Never used
Track 13 - Never used
Track 14 - The theme used as the lads are preparing to launch Dai-X
Track 15 - Never used
Track 16 - A theme I usually call Lamia's Second theme. It is first used in Episode 5 when the lads try to convince Lamia to return to X-Bomber.
Track 17 - The Ending theme
Hope that answers your question.
Pretty much when I should be working on college assignments. Not being a terribly social person helps too.
My memory is pretty clear with this after having worked on editing the episodes so much for the Remastering project.