Here is what to do:
1) Get the TREND data for the past 6 months..trend data takes the sales, inventory and other such data and gives you a eagles eye view of the marketplace. It is VERY important to know who your competition is, and how many houses are just like yours that have sold AND are for sale.
2) Get the list of ACTUAL SOLDS in the past 6 months
3) Look at HOW LONG these houses took to sell
Get all this real factual information from your Realtor...if your Realtor does not understand this terminology, find another...do NOT compromise getting this information.
Armed with 1 through 3, and analyze your home...looking at how low will you go to get your house sold relative to the competition..and what you need to do to your house to put in on the frontline in getting it seen and sold. Your Realtor can show you what you need to do..freshen up, do the curb appeal, etc.
Appraisers opinions are just that...opinions. Use real numbers in a real timeframe. When you list your house have means and methods to track how many people look / hit websites where your home is advertised. If your Realtor cannot provide that info, make them list the house on trulia.com and send you weekly updates as a minimum. This way you can analyze real traffic data to know if your house is priced right and if the marketing is working.
Selling your home is not a static proposition..you and your marketer/Realtor needs to put the word out and get immediate feedback from all sources...this is something an appraiser does not do..and the main reason you should not use their data for your purposes.