I think Denver 186 is exactly the same as the 188 but it doesn't play divx.
So I think it should be possible to put the divx firmware of the 188 in the 186.

Denver didn't release any firmware and I couldn't find it in the internet. Anyone knows where/how to get it?

And after that, how to put it in the 186? I know it is upgradeable via CD but I don't know how I could replace the entire firmware.

thanks
Pedro