The best replacement for solarwinds is nagios.

The best alternatives to solarwinds are rated as following:
★★★★★  nagios
★★★★  prtg
★★★★  whatsup gold
★★★★  manageengine
★★★★  zenoss
★★★  hp openview
★★★  opmanager
★★  scom
★★  splunk
★★  opennms
★★  vcops
★  shavlik
★  foglight
★  ciscoworks
★  sevone
★  zabbix
★  openview
★  whatsup
★  nagios xi
★  cisco prime
★  whats up gold
  netiq
  spiceworks
  secunia

Your alternative for solarwinds is not listed? Suggest!
Speaking about solarwinds, one probably shouldn't forget about sflow.

Other search terms related to solarwinds and their ratings are:
★★★★★ sflow
★★★ netapp
★★ netflow
★★ snmpv3
You have in mind a companion for solarwinds and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of solarwinds in all years. Click on graph for more.
solarwinds
nagios
prtg