Wifi antenna

Because i am planning for a new mobo, the mini-pici wifi card is replaced by a Alfa usb wifi.

Now i have an antenna from the mini pci car, its about twice as long as the the one that came with the alfa which is 2 db.

Looking for an antenna with a better db, i came acros this: Omni2 Car Antenne:
[media]http://www.2ghz.nl/components/com_virtuemart/shop_image/product/607b4fd36c9eaf5fa450fdecd022b43f.jpg[/media]

specs:
2400 - 2483 MHz
Kabellenght 2 meter
Gain 2 dBi
Dimensions 1 cm x 2 cm x 15 cm
Connector Type RP-SMA

now its only 2 db, but would it be better for use in the car than a normal wifi antenne of about 7 db or 9db?

I will mount it in the sunroof, next to the gps:
[media]http://img179.imageshack.us/img179/3383/gpsmc9.jpg[/media]

Never seen an antenna like that. Mounting it in the sunroof will kill a bit of your signal. Microwaves reflect off metal. The access points you're going to be connecting to probably aren't going to be right above the car.