What is a comfortable broadband speed for Call of Duty Multiplayer on Xbox Live?

Hello, I was wondering what you would each recommend as a comfortable broadband speed for playing COD multiplayer games over Xbox Live? I will hopefully be playing Modern Warfare 2 and Black Ops over it, fingers crossed....

I currently have just a 500kbps broadband speed, I will be connecting my Xbox to my wireless router via the Xbox wireless network adapter that plugs onto the back of your xbox. I've ordered it and it should be here by tomorrow.

Do you guys think I will experience any lag-free games? I don't really expect to, I don't mind the occasional bit, I just don't want it to get too annoying. Any speed reccomendations or could you let me know your broadband speed and how the game runs on multiplayer online for you?

And sadly I live in the middle of nowhere and I am over 5km from the nearest exchange, the speed won't increase for quite some time...

Thanks for any input, its appreciated :)