Intel Q6600 performance ?

Hi guys
im rebuilding my old socket lga775 based system as a spare pc ( or to use if my main sandybridge pc stops working ) and the pc is currently using a pentium E5700 with 4gb of ram and a HD5750
however ive been offered a core 2 quad Q6600 at a rock bottom price and was wondering is the Q6600 still a worthwhile processor ... will it run the latests games if i upgrade the gpu to something like the GTX650(or ti ) or has it seen its day ?
the strange thing is ive never owned a quad core .... my main system uses a pentium G620,8gb ddr3 ram and a GTX550ti ..... and all my previous cpu,s have been dual core and single core ( back in the days of the p4 and athlon64 3200 )
so how good is the Q6600 .... and what about the Q8300 ( which is avalible for £50 and the Q8400 for £60 ) ..... these are all used however the retailer is trusted and have a rigorous testing procedure ...
theres also the popular core 2 duo E8400 which costs just £40 ... any good ...
any feedback is much appreciated
( note : as i mentioned this is for a spare basic system for the odd bit of gaming )
cheers guys !