Not quite (d4x1.5)+1, 4 Missiles. Empowered Feat "Benefit: All variable, numeric effects of an empowered spell are increased by half." (Dont forget to round down the d4x1.5 before adding the 1 {2,4,5,7})
Magic Missile "For every two caster levels beyond 1st, you gain an additional missile, ... four at 7th, and the maximum of five missiles at 9th level or higher"
Technically speaking, roll damage for each missile separately, and increase each missile by 50%, rounding down. If you direct them at the same target, add them together, increase by 50%, round down.
i.e. the feat works better if directed at one target.
You also only check Spell resistance once, and only add bonus spell damage once per target.
No attack roll, however, unless you are using a 3.5 variant.
===Aelryinth
opps I was wrong FAQ "Empower Spell (page 122): If I use Empower Spell on a spell that has a die roll with a numerical bonus (such as cure moderate wounds), does the feat affect the numerical bonus?
Yes. For example, if you empower cure moderate wounds, the +50% from the feat applies to the 2d8 and to the level-based bonus.
—Sean K Reynolds, 07/08/11"
So 4 Missiles of (d4+1)x1.5 = {3,4,6,7}