Hi there, temps seem a bit high to me i have a 6800gt overclocked to 470/1305 and idle temps are 43c for the GPU and 31 for the pcb but under load these go up to 51c for the gpu and 37 for the pcb, i have mine on a dule loop with dule rad doing the cpu and single rad doing the card, take a look at my pics in water cooling under supreme-flow you can see what i have done there.
have you laped in the water block on the video card heat sink, if you havent then do this as it will help a lot with the temps.