If we could be sure the computer wouldn't get stuck (which is just a bug), then progress bars and spinners would be fine. If the task is as granular as you suggest, progress bars would be a great visual indicator, much better than text.
But since computers do get stuck, additional indicators should help with that. A spinner is supposed to show that a process isn't stuck, but those are fallible too. A textual representation ("bytes currently downloaded") sounds like a great addition to a progress bar. I've seen this a lot on linux distro installers, where you can click "details" below the progress bar to see the console output.