what he meant with the cpu is that 6 cores for games is not needed, most games these days only support 4 cores, and you can do better for the money you have, go look at the Intel i5 2500k but you will need a p67 or z68 motherboard, which would be about 120 dollars. hitachi hard drive is perfectly fine.
the graphics card you have is perfectly fine but if you know a bit about computers than with the price you could go with a ati 6850 crossfired meaning 2 6850's. but if you dont know what crossfire means than dont worry about getting it and that graphics card will do, also you need to go on the internet and find out what the best driver for crossfire is as some games dont like it.
try to go for a corsair 650 -750 power supply as they will never let you down.
and for the computer case try to go with a coolermaster HAF model as they would be the best bet for cooling and best cable managment for the price.
pretty much this is all you need to do with your system
this is the build i would suggest.
intel i5 2500k- http://www.newegg.com/Product/Produc...82E16819115072
intel z68 motherboard to go with the intel i5 2500k http://www.newegg.com/Product/Produc...%20extreme%203
btw the intel i5 2500k is a k series which can be easily overclocked because of the unlocked multiplier.
corsair tx750 power supply for crossfire 6850 or you can get a tx650 and save some money http://www.newegg.com/Product/Produc...82E16817139021
ati 6850 http://www.newegg.com/Product/Produc...82E16814125353
159.99 crossfire 319.98
which is more than the ati 6950 but you have saved money on the other products i have chosen which are better.
for the computer case you could get this awesome case http://www.newegg.com/Product/Produc...82E16811119233
for 60 dollars.
plus all the other things you want is a total price of $995 with much more incredible performance than what you had before.
but if you dont want crossfire 6850 than you can always go with this a gtx 570 which dominates a ati 6950 2gb http://www.newegg.com/Product/Produc...82E16814125384
which would make the total price of your computer 20 dollars more making it 1015 dollars.