Does a web site exist that either (a) ranks email marketing companies
(by some "fair" standard) or (b) allows clients to give their feedback
about email marketing companies in the "thumbs up/down" manner CNET
does with user opinions?

I'm mostly interested in part (b) b/c I want to read about client's
experiences with the companies, how they performed, etc.  Part (a)
would be OK if I knew the ranking was based on measured ROI or
client's input as opposed to some general Forrester or Gartner
research.

I am NOT interested in a list of email companies...I have found lists
and lists of email companies.  I have been through a handful of them
myself (I should start my own "email company ranking" site =]).  I DO
want to know which email companies are worth investing $10-$50k per
month in.

This is critical information for a web site I run
http://www.loan-place.com/ -- we feel we have pretty much maximized
our CPC advertising (Google, Overture, Lycos, 7Search).

Thanks.