When you updated the firmware, are you sure it was for the right model of burner? I don't know if it's even possible to burn the wrong firmware but you should double-check.
FYI, if a drive has the original firmware and will not play a commercial audio cd, then firmware is unlikely the main problem. That's decades-old technology. An audio cd is unchanged over the years. Even if the firmware was written 3 years ago, the drive will play audio cds. Firmware updates improve general reading/burning of disks and may for example allow you to burn at higher speeds or different disk types.
The drives must be communicating with the pc to get them into UDMA. The drivers will probably be standard MS. That just leaves reading disks as the problem. The lasers and drive internals have not changed since you started messing around.
After checking firmware installed, I would try disconnecting the drives (at the ribbon cable, do it one at a time for simplicity), reboot and allow to start Windows, turn off, reconnect drive, start up and allow new install of hardware. That should install the drivers OK. If the drive works, repeat for second drive.
Starman*