I had to select GeForce 7800, which is strange because I have an on-board 6100, but it will not work with the top NVIDIA option so 7800 is the only way I could get it to work.
I was surprised to see that I can now change video modes, though 16bit mode did not seem to help DOSbox from making the computer drag at all, though I only have 512Mb of RAM, maybe that has something to do with it?!
BOH's did not like it at all, I forget what I did, but it took forever to get it to display full screen again with proper colors and displaying corner to corner rather than only taking up half the screen.
I'm thinking AROS has some priorities that got over looked.