This is the latest version of the TS-431 on WOOT, listed under the computer tab. This is selling on Amazon for $400 right now.
http://computers.woot.com/offers/qnap-4-bay-diskless-workgroup-nas-1?ref=cnt_wp_0_4
They are also selling the TS-231+ for $189.
http://computers.woot.com/offers/qnap-4-bay-diskless-workgroup-nas-1?ref=cnt_wp_0_4
They are also selling the TS-231+ for $189.