I've got some nice input from customers about one piece of hardware I was not aware: The AtariVOX.

This little piece of hardware will be plugged to the 2nd Joystick Port of an Atari 2600 or 7800. It allows to output text to speech, load/store highscores and some additional soundeffects (including an amp as well).

Bad side this is not supported by any former game and requires current homebrew to be used (it suffer finally from the fact it is an enhancement of the hardware and do not improve existing one).

After a short review it outlines to be driven by a SpeakJet chip which is available for $25/item. This little chip requires very less connectivity and simple uses phonem to build the speech samples. The highscore feature works similar as the SpeakJet is controlled by a MCU. this chip filters the additional commands given by joystick signals and used it's internal nonvolatile memory to store the highscores. An amp and a simple "Vox" circuit for audio output completes the design.

In common nothing I'm not able to redo in better and cheaper technology 

I've made a quick test with an MCU and PCB I designed for an other customer in the past and by using a recompilation of the phonem converter of the Amiga with some sampled phonems the output is similar to the SAM software for Atari Homecomputers. It sounds also similar to the Intellivoice modul. The quality was ok despite some noise but this can be improved easily by altering the code and improve the sample rate of the phonem's.

Currently missing is an implementation of the SpeakJet commands (API) and additional funtionality. A test environment with AtariVOX ready games must also be prepared. Meanwhile development will take place with Stella Emulator.

An internal mod is the best option as external one require WEEE certification in europe and this is quite costly. Advantage is, that the audio inject is simpler (as it is required to mix the 2600 signal with the AtariVOX output audio). It is also possible to implement a selftest within the OSD menu.

As I use a common MCU (I currently think about splitting funtionallity by implementing two MCU possibly) the cost is not more than $25 for the whole mod so far beyond the originally version.