(Native American English speaker here.)
I don't think that the past-perfect tense emphasizes the length of time when the speaker was aware of the band but not hooked. It clarifies that the act of getting hooked happened in the past. If you use the simple past tense, like this:
I was aware of this band for a few years, but did not get hooked until I heard this song.
the time when the speaker got hooked is less clear. It might be in the present or very recent. The past-perfect version suggests that the speaker has been hooked on the band for a long time and is no longer experiencing the initial thrills of getting hooked, though context could override that.
If you wanted to emphasize the length of time when you were aware of the band but not hooked, you could put that at the beginning of the sentence:
For a few years, I had been aware of this band, but I did not get hooked until I heard this song.
Note that you need to repeat "I" to prevent this version of the sentence from becoming a little confusing.