If u did not start do start interviewing realtors to sell your property as you already worked for 5 years on selling it.
http://www.loopnet.com is a very good source for commercial real estate nationwide.
Not all commercial agents list on the 'standard' MLS. Many list on TCAR or Loopnet. Others use the good ol boy network. If your home is in a standard residential area, a place where normal commercial investors do not look, then a commercial agent may not do you any better.
As much as it hurts, there is a price out there for someone. But that would mean re-evaluating your asking price. I would recommend that.
Also, just as a side note, tax value has absolutely nothing to do with market value. This is not how appraisers or real estate agents or buyers assess the value of home and it is used solely by the county to determine what you owe them in property taxes, nothing more.