The only issue that I see in hiring an appraiser is this:
An appraiser does not normally quantify visual appeal of a property. If two properties are identical, and both in similar condition, on the same street, they likely will appraise for the same amount. However, if one has updated, current decor and the other is dated with old colors, most often the first one will not only sell faster, but at a higher price. A Realtor who is familiar with what is currently selling will have valuable input that an appraiser will likely not. Check out some of the popular shows on HGTV (Staged to Sell, Sell this House, etc.) to get an idea of the huge difference visual appeal makes for selling your house for the highest price.