as an update, it appears you should Mail the amended return since you Mailed the original return. just save yourself some time and mail it.
I personally wasted a lot of time tracking down an error because turbotax business does not yet allow efiling (due to an IRS publication not allowing it) an amended return. The IRS allows it for personal returns provided you efiled it in the beginning. Your choice, but efiling is so efficient and saves the government ( meaning us) $$ and helps reduce errors from the printed versions.
