The Letter Of Intent you accept will be the best deal you will ever get. Your selling memorandum, your recast financial statements, all your follow up communications with buyer and your tour of the facilities should all serve to justify your asking price. If the buyer has any objections or concerns about your asking price you want them to express them now rather than later.
An LOI is a nonbinding legal agreement that not only expresses interest, but typically details the initial terms for the contemplated transaction, timing for due diligence, any contingencies (financing, Board approval, etc.), and specifies the timing to execute a final definitive agreement and close the transaction.