3 devices and a hub is the first thought (Old School here)
firmtek miniswap/u3 is an interesting solution for 2.5 SSD - fast & many people on this board know about this review
http://barefeats.com/hard168.html
The 3.5s can be anything. Obviously, the Cal AV Pro is a great choice, but there are cheaper solutions that have an AS Media chip on board for speed.
Example - an HGST 4TB Deskstar is around 200 - a medium quality case can be under 100. The Cal AV in 4TB is 388 (Best price I know about for USB3 only) so it depends on what you need quality wise. Will you ever swap drives, etc? Oh, BTW a 1TB version of the AV Pro is 189 shipped, so it get's interesting on the low cap side of things.
Most pre-assembled externals don't have the best performing HDs, but they are cheap, so...?