Master Chief's coveted special edition 20GB Xbox 360, initially seen at Microsoft's E3 2007 press conference, is coming this September for $399.99, which is now $50 more than the Premium console. With that extra Ulysses S. Grant, you get an HDMI port, a headset, a Spartan green-and-gold finish (for console, controller and headset) and a Play and Charge Kit, according to the press release. The non-proprietary HDMI cable is sold separately.
Additionally, Microsoft's Aaron Greenberg has told us that the Halo wireless headset will be priced at $59.99 and will include some quality improvements over its predecessor. It will, presumably, also be deployed in September.