Comparison of OpManger to eHealth and/or SevOne

I am looking to possibly replace my current Concord eHealth (CA) product for a much less expensive one. I have looked at SevOne product and am looking at your opmanager product. Size of monitoring and systems I have are as follows:

Network Switches
4 - Cisco 6506 switches
4 - Cisco 4507 switches
4 - Cisco WS-C3750G-12S-E switches
42 - Cisco WS-C3750G-24TS-S switches
77 - Cisco WS-C3750-24TS-S switches
Total of appox 3000 ports.

Wireless Access Points
72 - Cisco 1200 Access points

UPS
27 - APC 1400 UPS RMNET
14 - APC 2200 UPS RM3U
3 - APC 2200 UPS RM2U
6 - APC 1500

Media Converter Chassis
8 - Lancast (Metrobility) Media Converter Chassis 7501-M SNMP capable

Servers
20 - Windows Servers
40 - Unix/Linux Servers

Desktops/workstations
800 - Windows Desktops
80 - Unix/Linux Workstations