I have a 340 S and I a m one of those hard of hearing old guys. Today I think I used robotic female but I had it at 95% and lost some quality. Any suggestions? Thank You!
You'll do best to stick with a female voice. The additional sound at the higher pitch helps. That's why, traditionally, most cop shops still use female dispatchers.
That said, you're stuck with the 340S speaker. One of the reasons I selected a GO model way back when was so that I could pipe the audio through the car's sound system. Sadly, both TomTom and Garmin are further reducing the ease of doing this on current models by removing the 1/8" jacks and/or FM from their units. The GO630 is the last recent model available in the US to support the 1/8" line-out jack. The GO740 should have supported it, but they required an accessory that they don't sell in the US to do it, although they can be found with some looking.
I still don't understand the absence of that feature on 99% of the current models. It's inexpensive to add, and can make a HUGE difference in the audio, especially in a convertible or other noisier environment.