The best card for the 6000 is the Intel PRO/Wireless 2915ABG; however, this card has been discontinued. If you can find one you won't be able to operate it under the Windows7 OS.
The latest driver for it is version 184.108.40.206 available from Intel's site.
The following statement came from their site:
The Intel PRO/Wireless 2915ABG Network Connection is no longer being manufactured by Intel, nor will Intel provide any future software updates to support new operating systems or improve compatibility with third party devices and software products.