If what I understand you are trying to do is correct, then there are at least a couple of ways you could do this.
1) Use Report Writer to create an inventory of all your nodes, listed in order of IP address. Add the appropriate matching criteria for SNMP in the report. Compare your report to the scanned subnet.
2) Use the System Manager to create a new view (System Manager -> View -> New View) and choose the items you want to show in the view (IP, Community Name, Hostname, etc.). You can then export that data to an excel spreadsheet and compare it to your other data.