http://www.kickstarter.com/projects/kwa ... i-fairywre
with a PC power unit you can power quite a few.
you cannot get a SATA to USB cable - you will need an adapter of some description. however
3.5" external caddies will have them - just remove the gubbins and power them all from +12V line off the PC power...
get a Mini ITX case and PSU to do it all ....
I've got a 3.5" external drive case with a Raspberry Pi and a 2.5" drive and USBhub in it .... it's a bit messy with wires all over the place but it works and is all powered from the external USB HD adapter