How far q6600 should go with stock fan?

Hello,
i have an asus p5qc and intel q6600 with 2*2gb ram @667mhz.

i have read thread about overclocking this setting. i understand that the ram isnt so good. i wont be paying more on this useless board except for parts i could use for my next rig.and another point is i cant buy any good heat sink here in my country. so my question is: how far can q6600 go with overclocking under my setting(stock fan)?

i would really appreciate your suggestion. juz 2.8 would make me smile.