Where is the best place to get 300 Whipser dies?  I know several companies make them, but is there a brand and supplier that you guys prefer?

I ordered 300x221 dies made by Redding from Midway USA.  300 Whisper is registered to SSK Industries, so they are the only ones that make dies that actually say "300 Whisper" on them.  300x221 is the "generic" name for them.  I think there is some minor variations in the dies, so it will depend on whose upper you have.  Randall is making mine, and the Redding dies work well for his setup.  If you have an SSK barrel, I'd get the SSK dies.