bgillett,
Thanks for the photo. While the difference in reported gross living area and the discrepancies in opinion of market value between the 2 appraisals would give me some cause for concern, as the one which represents the subject as being 1000 square feet larger also has an opinion of market value $6000 less, this could be explained if they appraiser(s) explained in detail why the felt the pool room should/should not be included in the gross living area and how they reconciled the opinion of market value. If the explanations and research performed were sufficient, as opposed to just arbitrary, what you may very well have are 2 appraisals were each appraiser actually gave consideration to your pool room, just reported it differently. If that is the case, what you really have are 2 appraisers who came up with an opinion of market values less than 4.5% apart from each other on what apears to be a unique home and very well a complex assignment.
My next comments are directly specific to my market and may not at all apply in any way to your market. You mention that the upper end of your market is $150K. Now in my market and socio-economic environment, $150K homes are located in neighborhoods and appeal to buyers/families where the burden of maintaining an indoor pool, while maybe a desireable amenity, may not be feasible due to overall costs associated with year round running and maintenance. The pool may, to potential buyers, be seen as something adverse, as the family budget simply does not permit them to maintain correctly, which then leads to additional problems. Just food for thought.