My 9800GTX is overclocked to about GTX+ speeds. I get 4200 for 511s, 6600 for 353s, 5600 for 1888s, and various other numbers in between. Here's a thread (had to find the sucker) that has a nice database in it. The actual link to the database is here. It seems kind of large though, lots of detail but not too easy to navigate. At any rate its got tons of numbers.