One way to modify solution 2 to work with the mentioned operators (=, <>, > , <, IN) is to create the WHERE clause like this:

WHERE (A.name = @Aname or @Aname = '') and (C.firstName like @Cfirst or @Cfirst = '') and (C.lastName like @Clast or @Clast = '') and (D.city like @city or @city = '') and (D.state = @state or D.state = '') and (D.phone like @phone or @phone = '')

This solution removes the assumption that a NULL record is included. It also means that if you do not want to limit the result set by a city name simply send in @city = '' and that part of the WHERE clause will be completely ignored. It will just limit the result set on all other parameters that are not equal to ''.

Robert Marda