I'm a little surprised by all these responses here, I expect more support for the FX5900. In an overclocked situation the 5900 should perform better overall, but the R9700Pro probably keeps the advantage with shaders and AA/AF (something Nvidia really screwed up in the FX series).
The other thing I don't like is your chocie of FX, the OTES is one frigin loud card. It's the same design as the FX5800 dust buster. So between those choices, I also agree the R9700Pro makes more sense.
If you have picked a different FX5900, with a sleaker design and still overclockable, I might have vote differently.
So why am I using the FX5900XT and not a R9700Pro? Because I like Nvidia drivers better (nView, digital vibrance)