let me preface this by saying, i know nothing about cars( aside from the basic what engines do etc.)

i have a 07 WRX tr with stock everything. I decided i wanted to change my headlights, and i understand the stock WRX headlights are 12v 55w h7 bulbs.. After a quick google search they were selling for roughly 5bucks a bulb.

the WRX-STi bulbs stock (12v 35w d2s) blubs sell for 50 per ..

here are my noob questions. I already have housing for HIDs? or would i need to buy an HID conversion kit? could i just buy some WRX sti blubs and plug them in and be done? i understand the wattage difference, however is it small enough to matter with a plug and go/swap out? i am jsut trying to find a starting off point. any advise or pointers would be helpful.

 

ok, after a bit more research i found that the D2S is the housing for the STi lights? how is that any different than my h7 fittings?