If you want my advice, change both your low beams and high beams. The low beams are a good increase, but the real majesty of the Silverstars comes from the brights, trust me.
The numbers you see 9003, 9004, 9005, etc. all represent the bulbs that fit certain cars. If you look in your owners manual for replacing the headlights, it will tell you what the number for the low beams and high beams are.
I would recommend the Silverstar Ultras for both low and high beams.
Hope this helps.
EDIT: The Civics use 9006 bulbs for the low beams and 9005 bulbs for the high beams. I would use Silverstar Ultras. The regular ones are good too, but the Ultras appear to be brighter, I've used both. Avoid the "Cool Blue" ones like the plague, they aren't blue at all and the light output is pathetic.