Sandy Bridge's biggest advantage is that it has an integrated memory controller and not connected via an FSB. The FSB is the biggest drawback of the Q6600, if you leave it at stock 1066, its actually right on par with the i3-2100.
but the q6600 especially a low vid G0 is a monster of a chip.
Just look at this thread! http://www.overclock.net/t/1376341/how-many-of-you-have-actually-killed-a-q6600
I was just playing with one and on a P965 mobo took it to 3.0GHz with out blinking an eye, only reason I didnt keep it was because there was some killer deals on Z77 mobo and an i5 3570K, 16Gb Ripjaws for free, $40 bucks off the mobo, I couldnt say no.
I just sold my Q6600, but I definitely recommend it.
They are going for $60 on ebay shipped, and will probably just slap right into that 775 motherboard, weather or not your can overclock it well will depend on the mobo. Even the B3 stepping chips see 3.0GHz easily.
Edited by TheProfiteer - 4/4/13 at 11:50pm