Ed,
    I agree with your perception of 'real' clean rooms in other board shops.
 Other than trying to impress people touring your facility, a certified 10K
or 100K clean room may not be worth the ongoing expense.  It depends on your
shop's processes.
    In your situation, you may want to include into your plans, space for a
certified clean room.  Before you commit to a certified clean room you need
to be able review the types of in-process defects that you are having.  If
that information is not readily available to you, then your best investment
at this time is to set up a data collection system so that you can review and
monitor your in process quality.  You NEED to know what type and the number
of defects you are having.  Without being able to see what your process is
doing, the chances of spending your money on value added process improvements
are slim.
    Once you have a data collection system in place, the need for a clean
room (or other capital investment) will be obvious and justification will
then be easy.  It would also allow you to set up your clean room to suit your
needs without overkill.
     Norm Dill