Sorry for the lack of posting - I'm adjusting to the new schedule and workload.
The gemara (Shabbos 23b) writes that if one has only enough funds for either kiddush or Shabbos candles, Shabbos candles take precedence because they serve to enhance shalom bayis. The Nishmas Adam (klal 68) asks: why do we need the justification of shalom bayis as a reason to favor hadlakas neiros?-- there is a much simpler reason to do so. The gemara in many places has a rule that "ain ma'avirin al hamitzos" -- one cannot pass over and ignore one mitzvah in order to fulfill another one. Since the mitzvah of lighting shabbos candles applies while it is yet day and the mitzvah of kiddush does not apply until night, withholding funds necessary for the earlier mitzvah of hadlakah to fulfill the later mitzvah of kiddush would violate this well known principle.
R' Yosef Engel answers that the mitzvah of hadlakah itself in essence applies only at night, but since it is impossible to light candles at night they are lit earlier on Friday afternoon. The hadlakah is just a hechsher mitzvah to establish candles burning on Shabbos. If not for the justification of shalom bayis this hechsher of lighting would be no more significant than the hechsher mitzvah of buying wine for kiddush.
This answer of R"Y Engel contradicts a Brisker torah which we discussed before on the blog. The Rambam records the mitzvah of hadlakas neiros Shabbos both in chapter 5 as well as in chapter 30 of hilchos Shabbos. The Brisker Rav explained that there is no redundancy in the Rambam; rather, there is a double kiyum mitzvah in lighting shabbos candles. The Rambam mentions hadlakah as an aspect of kavod Shabbos, of preparing and welcoming the Shabbos by our actions before Shabbos, and the Rambam repeats the need for candles to be burning as an aspect of oneg Shabbos, the mitzvah of enhancing Shabbos on Shabbos itself. If this is correct than the lighting of candles on Friday is not just a hechsher mitzvah to have light at the table on Shabbos, but is a mitzvah act in itself.