Wow ... i never knew that you couldn't flash the bios on nvidia ... Have never bought nvidia for anything! Won't as long as i have a choice.. seems like such a "dirty pool" kind of company.
For intense, it seems to me AMD is better
For AMD, there are options for changing the memory timings. For NV I did not find this. The chip itself can probably be reflashed. The only question is where to get a modified BIOS.