I have a ScanSnap1300 on my desk which works like a dream - I have stuff go direct to Evernote.

There is a network version for £1300, but I would think hard about whether you need it and where you want to keep the finished docs. A single scanner attached by USB to a computer can be configured to dump the PDFs to a network drive, thus accessible anywhere in the office for a lot less than a networked scanner. You can even buy a couple of scanners and have some redundancy for the price of an expensive network box.

Another alternative may be to use an HP All-in-one: the scanner can be set-up to send the output to different machines on the network, but you won't get the duplex and speed of the scansnap.