@reshtheory
Welcome to GPS Power. If the 1390 is booting up and working but is mute when navigating then it's definitely not bricked. Cure firmware is only useful to enable Mass Storage Mode in devices which can't boot fully because of corrupt files not loading. Once MSM is enabled they can be deleted or a re-format can be done. There are a few possibilities why it doesn't have voice for navigation:
(i) If it also doesn't have any other sounds such as key tones when selections are made then check it's not set to mute or very low volume on the Volume page.
(ii) If the Volume level is set ok with no sounds at all then there's likely a hardware problem.
(iii) If it has tones for selections, maybe there's no VPM voice files loaded as you suspect so check in Tools>Settings>Language that there's a voice selected or look in Mass Storage Mode connected to a PC that there it are proper*.vpm files in the root folder named 'Voice'. You should be able to replace missing VPM files by connecting it to GarminExpress or WebUpdater.