As we reported you that Redsn0w 0.9.6b1 is loaded with major updates. Redsn0w 0.9.9b1 won't ask you to choose ipsw file when you jailbreak your iPhone, iPod or iPad as it will automatically detect the best solution for you (tethered or untethered jailbreak).
The only case that you will be asked to point to ipsw file is in iOS beta versions as it isn't available for public. Redsn0w 0.9.9b1 will allow you to verfiy / submit your SHSH file to Cydia. Below you will find all new features of Redsn0w 0.9.9b1 officially from iPhone Dev-team blog.
A bunch of new features!Here's how to use Redsn0w 0.9.6b1 :
Download Redsn0w 0.9.9b1 for Windows
Download Redsn0w 0.9.9b1 for Mac