What kind of information do you want to collect?
up/down status
Interface errors
status of bandwidth
faults
device status (CPU, memory, buffer utilization)
Config change/control
If you are looking at simple network traffic and you have a Cisco pure environment, Ciscoworks is good. I forget which package has it, but I think it is Ciscoworks for Windows which includes What's Up Gold built into it. It should cost you around $2800 depending on the deal you can find.
HP Openview Campus is your next choice. It exchanges the configuraion management functionality with a slew of other bells and whistles to include event notification and alarming. Its the dog, but you will only be able to manage 250 nodes, not a problem with your network it seems.
Of course, if price is the issue and you want something simple, Mike is correct with his assessment of Solarwinds as a good choice.
Blaine