Not familiar with superbiiz, but that's the one to match (though it probably cools better..different fan placement). Remember that both 5850's don't need to match vendors, and that you could easily get an ASUS 5850. Their CuCore series is extremely good at cooling and overclocking, should you choose to do so.
IF you do that you'd be wasting the 1GB of RAM (in crossfire they can only use the same amount of RAM !) better to save some $ and go with something like this XFX for $180 after MIR - since it is the same clock rates and memory config as your current board ! ( it is also a reference board so pretty much the only difference between them is one is sold by XFX instead of Sapphire and the fan\shroud are a bit different)