With these hybrid setups you'll still always be wasting the difference between the size of the largest drive and the next largest if you're only replacing a single drive in a single drive redundant array.

Put simply, adding a single drive to the system that is bigger than all the other drives will not increase your usable storage space. You will have to swap two drives and the space gained is about equal to the difference in storage of the smaller of the two over top of what it's replacing (if the two replaced drives were the same size to begin with).

It's the same for ReadyNAS' XRAID and Dobo's DroboFS.

Tony, I like the look and functionality of the "classic" SqueezeBox 3. If you don't think you'll need a display at all, you might go for a SB Receiver. Otherwise the main advantages with the Touch are that it's controllable right from the unit itself and it can also run a mini-server allowing you to connect storage directly to it.