1. A system that enhances the performance of an existing cochlear implant using a hearing aid preprocessing device, the system comprising: said hearing aid preprocessing device comprising: a plurality of hearing aid signal input devices, comprising one or both of a hearing aid microphone and a hearing aid telecoil, a first processor coupled to said plurality of hearing aid signal input devices for performing signal processing on signals received from said plurality of hearing aid signal input devices; and said existing cochlear implant comprising: at least one cochlear implant signal input device, comprising one or both of a cochlear implant direct audio input and a wireless receiver for receiving said processed signals from said hearing aid preprocessing device; a second processor that processes and encodes said signals received by said at least one cochlear implant signal input device, a transmitter for transmitting said processed and encoded signals to an implanted portion of said existing cochlear implant; wherein said existing cochlear implant is retrofitted with said hearing aid preprocessing device by communicatively coupling an output of said hearing aid preprocessing device with one or both of said at least one cochlear implant signal input device of said existing cochlear implant, and wherein said hearing aid preprocessing device comprises a compatibility matching circuit coupled to said first processor for adjusting the processed signals received from said first processor to match at least one signal requirement of said existing cochlear implant.