Thank you very much, that is helpful indeed. I searched across old forum posts and the most I got to was that lower devices like 2x5 use the 'RealSpeak Mobile' TTS engine whereas the higher end models use 'RealSpeak Solo'. There was otherwise very little information about these on the web in relation to Garmin GPS. Even information I gathered about RGN files were limited. Only now do I know about that RGN_Tool thanks to you.

From the voices in that site I gave, I think I may have already tried at least one TTS, TTS2 and TTS3 file (I might be mistaken) without success. So now I'm very curious what TTS version is the one for my model series.

Thanks! I am looking for TTS British English (or Irish, if it exists?) voices, I haven't actually heard all of them so I'd want to see all.