Not exactly. The NAS device I linked is essentially a small computer that you need to buy a hdd separately from your favorite hdd vendor. Squeezebox server is installed on this device and with the hdd I install it will be both a network storage device and have the ability to stream to the SBT. Squeezebox server doesnt run on the touch.
I do not think you are right. When you attach any storage device to a touch, the device acts only as storage, not a server. If you select USB as your music source then the touch will run its own version of the software to access and play the music that resides on the external drive. If you want the touch to access the music through the network then the NAS doesn't / shouldn't be attached to the touch via USB. The NAS can be anywhere as long as it is attached to your network. That is the whole point of the Squeeze system. I have a Touch, a SB3 and a Transporter so I have tried all these configurations.
If you are interested in hi res then you need to assess the processing power of the NAS if that's where the Squeezecenter software will run. I have opted to use a PC since decoding 24/96 flacs takes a bit of power.
I agree with the comments about the power supply. The stock power supply is crap. I have used the Channel Islands audio P/S successfully.