For anyone who's interested, I've tried Elcomsoft Distributed Password Recovery software v. 2.71 build 195, and it's actually pretty decent. I'm using an Nvidia 8800 GTX overclocked to 575Mhz (this is now old technology compared to the 9000 dual GPU units), and it processes about 4000 passwords/second. If you're running dual cards with dual GPUS you can expect some excellent rates.
The software is also pretty versatile, it allows you to choose the parameters on brutreforcing: for example, you can set the number of character in the password, which character set to use (lower case, uppercase, digits, special characters), and it will systematically go through all combinations. You can also set "masks" , that is, if you know any parts of the password (definitely) then you can enter them to reduce cracking time. With a GPU setup, you can feasibly crack 8 character passwords within a few weeks of computing time.
The software also allows the use of servers and agents to assists in the bruteforcing. Its actually a well designed piece of software imo.