The enforceability of a covenant not to compete in Georgia is too complicated to advise a client over this website. Covenants predating the new law are difficult to enforce because if any portion of the agreement was unenforceable - the whole covenant was unenforceable. If this is important to you, which it sounds like it is, you should contact an attorney and let him or her read the agreement. An experienced employment attorney should be able to sit down with you, review the contract and advise you in less than an hour. Many law firms, including this firm, would be willing to schedule an appointment for this purpose. Good luck.
First, the new law does not apply to old contracts. Second, the old law requires that a covenant not to compete be reasonable in three areas: Duration, Georgraphical Limits and Scope. Georgia courts have routinely held 2 years to be a reasonable duration. The questions in your case is whether the extremely wide geographical area is reasonable. In addition, the scope would be unreasonable if it prevents you from doing anything for a competitor that you have never done for the first employer. These are the types of questions that are worthy of a good legal consultation. www.nela-ga.org is a good source to find employment lawyers in Georgia.