Which Multiplayer FPS?

Hey guys.

It's been a while since my last visit, but have once again came for guidance.

I'm looking inot starting some serious FPS online. Except i'm having troubles looking for a game to choose, to get into.

The features i'm wanting are:

- Clans
- Heaps of players
- Be able to communicate with a mike (doesnt have to be built into game)

Also it would be nice, but not a nessesity to have a game that has a online play crack, so i can download and play.

But worst comes to worse i might just pay.

Im realing looking into COD4 of BF2. Don't really want counter strike, but am considering.

And not Crysis, unless someone can back it up by telling me it has really intense online play (with many players).

My Specs:
Amd 64 2x processor ~2.4 Ghz
3Gb Ram
256 Graph Card NIVADA
20" LCD

Fill me in, thanks guys.