I've got the core on mine running at 395 right now but I'm watercooling it. Now some of the ones with the big copper coolers like the Leadtek will hit that speed on air with no artifacts but I doubt that you'd get that speed out of one with the stock aluminum reference cooler very easily, but, I could be wrong.
As for the memory, you'll be hard pressed to reach more than 830mhz with it considering that it's DDR1 and usually rated for 850mhz but running lower voltage.
If you were to get the ASUS 6800 gamers edition it more than likely would be able to hit GT speeds as it has 256Mb of GDDR3 but why bother? It costs as much as a GT does anyways and still only has 12 pixel shaders and 5 vertex shaders.
I hope this answers your question.
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As for the memory, you'll be hard pressed to reach more than 830mhz with it considering that it's DDR1 and usually rated for 850mhz but running lower voltage.
If you were to get the ASUS 6800 gamers edition it more than likely would be able to hit GT speeds as it has 256Mb of GDDR3 but why bother? It costs as much as a GT does anyways and still only has 12 pixel shaders and 5 vertex shaders.
I hope this answers your question.