Available at:

• $99 - http://www.amazon.com/Vantec-3-5-Inch-External-Enclosure-NST-640SU3-BK/dp/B007XJIYI6
• $126 - http://www.ebay.com/itm/Vantec-NST-640SU3-BK-Quad-3-5-SATA-to-USB3-0-and-eSATA-External-HDD-Enclosure-/261011141852

Mediasonic Pro Box enclosures

4 disks, USB 2.0 - Mediasonic HF2-SU2S2

Available at:

• $99 - http://www.amazon.com/Mediasonic-HF2-SU2S2-ProBox-Enclosure-Drives/dp/B002UUPWP6/ref=sr_1_5

4 disks, USB 3.0 - Mediasonic HF2-SU3S2

It has simple and RAID versions.

Available at:

• $119 - http://www.amazon.com/Mediasonic-HF2-SU3S2-ProBox-Drive-Enclosure/dp/B003X26VV4/
• $216 - http://www.amazon.com/Mediasonic-HFR2-SU3S2-ProRaid-External-Enclosure/dp/B003YFHEAC/

8 disks, USB 3.0 -Mediasonic H82-SU3S2 ProBox

Available at:

• $269 - http://www.amazon.com/Mediasonic-H82-SU3S2-ProBox-External-Enclosure/dp/B005GYDMYG