Gabe, you're missing the third dimension =) The circular area on that mono-filament is probably close to being the same as a half inch wide copper trace in effective circular area, with higher surface area for high frequency signals.
As far as audio bass goes... You don't use traces.... You use the thickest wire that you can practically use in your application. If you want punch you need massive capacitor banks for short term power. You can't sideline the details, the 'bass effect' isn't an effect, it's a consequence of systems designed for it, a bass spike that's audible that can be felt in the chest contains a MASSIVE amount of power compared to even a quiet mid range note.