The temps are fine, but if you reduce the fan speed they will go up.
Must admit the fan on my 7900gs xxx annoid me, but only when playing games when it would speed up.
I got a aftermarket cooler, it's a gigabyte one, basicly it is the same cooler as the stock one from the 7900gtx
something like
this would work well
if that's too much to spend then I picked mine up from ebay for £15 delivered so have a look and you might find something good.
(remember that replaceing the cooler does invalidate the warranty.