Seriously, find a local realtor who can guide you through this needle eye art form.
In my own home community of Oshkosh we had a full community appraisal about three years ago during the height of the housing boom. Our appraisal fall off might be more significant than other communities. On the other hand, homes in my neighborhood are up a little over our appraised value.
A local real estate agent can research the neighborhood and current market to get you the number you are looking for on this particular property.