I am looking for a stand alone hardware appliance that will sit in
between my internet router and my network switch that will do internet
bandwidth monitoring. We have about 60 computers on the network.  If
the internet is running slow, I want to be able to view who is using a
lot of bandwidth and slowing everybody else down.

Requirements:
1. The appliance is not required to control the bandwidth nor filter
sites, only show me who is using what bandwidth.
2. I need it to cost $500 or less.
3. I need it to do network name resolution so it will show me the
WinXP computer name and not just the IP address.

I think this could be solved with a computer running linux and two network cards.

Then again I might be wrong.

I don't think you need a device to do this....and I think I can offer
a way to accomplish this task at $0 cost.

I would suggest visiting http://www.openxtra.co.uk/downloads/index.htm
and downloading their free windows versions of MRTG and/or NTOP.  NTOP
is most likely the tool you will need NTOP program since you will need
to track things back to the IP and PC name.  The program will need to
be installed on a Windows PC, preferably a server or a machine that is
running all the time.  The machine will also need to be plugged into a
switch or hub which also has your internet router plugged into it. 
The NTOP program will basically watch all the packets that go by and
complie that information into a database which can be displayed by
accessing a web page.  It can show traffic by type, port #, user, IP,
MAC, name, etc.

I hope this helps and let me know if you need further explanation.