Newish radio isn't loud enough

Check that the impedance of your speaker is correct for the new radio.

Another thing to consider is where the sound is coming from. I have found that speech is more easily processed when the source is located in front of me rather than behind. I have moved my radio speaker to the panel. I can hear it much better there than behind my head. Panel space is precious, of course; yet for me, the benefit is significant and worth the price.