Funny, I've got no complaints about the sound quality on TZ. If i step back and try to analyse the sound quality, I can recognize that the quality is lower, but I feel like it has no impact on the game. If I didn't know otherwise, I wouldn't have realized that it didn't use the same sound system as my No Fear.

You should be able to clearly hear "I'm Talky Tina, here's your extra ball!", followed by the sound effect and creepy giggle (the best is when that shot starts multiball, because the machine turns off the music as soon as you hit the shot, but doesn't start the multiball music and sound effects until after the EB sequence, so you hear Tina against a background of silence; the laugh is haunting.). If you can't, there's something badly wrong with your sound system.

First things i'd reality-check with is to see if it sucks equally regardless of the volume, and whether the music and sound are both crappy, or just the sound effects.

I would not go ahead with a speaker mod if the sound is such that you can't make out what Tina is saying when you get extra balls. That should be intelligible (sure the quality isn't that great, but you should be able to hear what she's saying), and if it's not, i'd be concerned that there was a problem with the sound boards/roms/etc.

The last thing you want is to upgrade the speakers, and more clearly hear a glitched voice sample.

I didn't think the DCS systems used different speakers - do they? I thought it was just the electronics driving the speaker (with DCS systems supporting higher bitrates and hence producing better sound).