That 3200 lumen rating you see is for two bulbs. So, it is only 1600 lumens each.
...which is still a gross overstatement of the amount of light each bulb puts out on initial power-up, let alone after they've run for 10 minutes...or half an hour. All of which is irrelevant, because:
LED retrofits do not work
Correct. Headlamps are not flood lights. They are precision optical instruments designed around a light source of a particular, specific shape, size, position, etc. Swapping in a different kind of light source (HID or LED instead of filament) destroys the beam pattern, thus destroying the headlamp's safety performance.
HID is your best bet as Subaru has HID headlight housing for your Imprezza
The original poster has an Outback (a Legacy model), not an Impreza. If HID headlamps are available as an option on the '15 Outback, installing them would be the best possible upgrade, and would unquestionably maintain the vehicle's warranty. An "HID kit" in the halogen headlamps wouldn't, and it would also be unsafe and illegal. An H9 bulb (2100 lumens) in place of the H11 bulb (1350 lumens) in the low beam would be safe, effective and (arguably) legal.
Also, the original poster is in Virginia which has a pretty strict vehicle lighting equipment code, and law officers and vehicle inspectors happily ticket for installing "LED bulbs" or an "HID kit" -- yet another reason why doing so is foolish.
As for the "Morimoto" idea: why would you vandalize your brand-new car with
that junk?