First, I would like to say that as far as I know, there are no upgrades available for the Denver DVD-176!
If you do not know what you are doing, please do not try to change the firmware in your player. If it goes wrong, your player will be unusable!!!
If you would like some more information about the firmware in the DVD-176, please look at the EuroLine 6620 firmware page, as much of the things that are written there probably also applies to the Denver DVD-176.
If there will ever be an upgrade for the Denver DVD-176, you will probably be able to upgrade the firmware in it by making a CD with the firmware binary on. I am not sure what the name of the binary file on the CD should be, maybe BANK30.ROM works for the DVD-176 too.
These are the setting that probably can be used in Nero (v5.5.9.0) to make such a CD:
When the CD is ready and inserted into the Denver DVD-176, it will hopefully update its firmware automatically.
As I have not been able to test this, I cannot make any promises that this is the proper way to update the DVD-176 player. But as it seems pretty similair to the EuroLine 6620/6650 / United 3151/3155, this method will hopefully work!