Steam Machine will be available in GameStop and EB Games.
Valve has made a partnership with GameStop (US & UK), and EB Games (Canada). These companies will be selling the Steam Machine’s hardware in their stores. “Steam Sections” will be created in the retail stores sometime in the fall. The Steam Machine and it’s hardware will be available November 10th.
GameStop, EB Games, and GAME will be exclusively selling the Steam hardware. These companies also happen to be the some of the biggest gaming retailers.
During the first wave of pre-orders for the Steam Machine, the hardware sold out in less than a month. The first people or pre-ordered in the first wave will be getting their devices on October 16th. Other people will have to wait till November 10th. Pre-ordering Steam Link or a Steam Controller will grant you a digital copy of Rocket League and Portal 2. If you have one or both, you can get the copy(s) as a gift for your friend.
The Steam Machines can be purchased through steam or the retailers stated above.