IIS 7 Perfmon Counters - What should I monitor to see if my website needs more horsepower?

Hello,

I have a (2) node WLBS IIS 7 Webserver cluster running ASP.NET native applications talking to a SQL backend (SQL 2008 R2).  I want to monitor the IIS counters and any applicable adjacent counters to see if my application and/or server needs to be tuned for optimal performance.

What should I monitor?  I can't seem to find a best-practices article for monitoring IIS in general, but I was thinking of creating a data-collector set in PERFMON and monitoring:

- WEB SERVICE:
   - anon users/sec
   - bytes recd/sec
   - bytes sent/sec
   - bytes total/sec
   - cgi requests/sec
   - connection attempts/sec
   - current anon users
   - current connections
   - current non-anon users
   - get req/sec
   - header req/sec
   - isapi extension req/sec
   - total bytes rec'd
   - total bytes sent
   - total bytes transferred
   - total connection attempts (all instances)

W3SVC_W3WP
   - active requests
   - active thread count
   - requests/sec
   - total threads

Processor
   - % Proc Time

Memory
   - % commited bytes in use

Physical Disk
   - % Disk Time
   - Avg Disk sec/read
   - Avg Disk sec/transfer

Anything else?  Should I NOT be looking at these?  What is the best way to see if the web server is running optimally and does NOT need more WLBS nodes and/or a balancing appliance?  

I hear users complain that the application could be faster, but they don't say that it's exactly slow, and I'm happy with the speed that queries are returned...so I need less subjective results and more objective results.  

Ideas anyone?

Thanks!