My guess is that you will have to sign a release in return for the "couple thousand more." By signing it you will likely be forfeiting the right to sue. The release will probably have a title like "Severance Agreement," but in reality the paragraph or two that say you can never sue the employer is the main reason for the document. It will also say that the company told you to get legal advice from an attorney before signing. You should really consider calling an employment attorney to review any agreement they want you to sign.