Virtual Machine Sizing

I have a few end-of-life servers with apps consolidated on them. Most of

these applications can probably be virtualized to save $$$ on new servers.

Server1 hosts:

Symantec antivirus 10.1 (server for @ 100 clients) (virtualization possible

here?)

A low-load MSDS IIS website (maybe a few users per hour, just used for

safety reference in case of a fire, spill, etc.)

Server2 hosts:

SQL 2000 with @ 15 low-load databases - will not virtualize

Websense Enterprise running all services with network agent (potential

virtualization)

IIS company intranet..simple, low-load

I would like to capture performance logs on the above servers in order to

better "size" for my virtual environments. Any ideas of how to best

configure that? (counters, etc?)