Determining ARV on one-of-a-kind property in a neighborhood.

[Dave G.]

Hi Rehabbers and Flippers- 

I am trying to determine the ARV on a property that is unique within its neighborhood and could use some help. I'm a new RE agent, so I have access to my local MLS and have been looking at sales and listings to try to determine good comps. Unfortunately, everything in the immediate vicinity is much much smaller than what this property is; 500 - 1000 Sqft smaller (it's a rather large duplex I want to convert to a SFR). All of the lots are smaller too, much much smaller. And to make things worse, there is a neighborhood 2 blocks away where this house would be more at home, but still probably be the largest lot and the largest house.

   Is it reasonable to expand my search to this neighborhood despite it being a historical neighborhood with national recognition? There is another neighborhood further away where almost every house is a 4000+ Sqft 5+ bedroom mansion, but it also has a specific draw to to its name. All of these houses/neighborhoods are from the first few decades of the 1900s. 

  Tl;dr - Is it unreasonable to stretch a bit further for comps into neighborhoods that have the draw of a well-known name that my property obviously wouldn't receive?