question on overclocking

I just installed an asus oc en9500gt earlier today, and after reading about how much the 9500 gt can be further oc'd, i opened up the smart doctor that came with the drivers, and tweaked some settings. i upped the shader a bit, raised the engine from 600 to 700, and raised the memory from 1800 to 2000. i was running a game at the time, and i have not seen any artifacts or anything of the like. So my question is: are those setting okay to run at? if anyone has any advice concerning this, id much appreciate it. I turned the settings back to default until i can get a proper answer.