Upgrading the sound is awesome but it does have some annoyances in the form of rattle.
- Electical tape/more glass friendly tape on the edges of the playfield glass keeps it from rattling
- Foam stickers where the speaker panel hooks keeps that quiet
- Thinner foam on the plastic edge on the translite to keep that quiet
- Some dynamat stuck to the sides of the cabinet inside for good measure as well wouldn't hurt
You could go external sub, but I prefer to keep pinball things inside the pinball cabinet. Plus when the entire cabinet is your subwoofer box you can get some pretty good sound.