I wouldn't personally go with the Q6600 or the E6550 ,why not go for the E8400 ,you can OC it to 4.0ghz easily and get alot of performance out of it .and even if you get the quad or the E6550 ,and get the 8800GTX ,you cpu will be bottlenecking in maxxed out graphics and physics ,as for the RAM ,this is good but if you intend to OC then i would recommend the Corsair Dominator 2gb @ 1066mhz - 6000 Rs ,mobos are good ,but if you can then go for the P35 Neo ,mouse is also a good choice .
For now ,nothing can beat an 8800GTX or 8800GTS 512mb *.
the GTS 512mb because in some lower resolution cases it can and it will outperform the GTX but in high res cases the GTX is a better choice cuz of it's bigger bus width - 384bit .(high res - 1920*1200 ,lower res - 1440*900 or lower)
* Any Single Card Single GPU Solution can be beaten by these two .
according to my speculation ,you WILL last for abt 1.5years ,but not more than that cuz of the lightning speed at which technology is moving forward i.e 9900series and HD 4XXX and the NEW NEHALEM FROM INTEL N ALL