hey omar, well I read your post and skimmed the rest of what everyone wrote, anyway if you wanna read about pc vs consoles we discussed it before in
this thread...
anyway let me help you out, since you want your pc for gaming, you need to focus on what to buy for graphics card and power supply, the rest is not as important as these are...
my rig is:
2.2ghz dual core
3gb ram ddr2
for vga: 1gb gts 250 (nvidia ofcourse)
and for power supply a thermaltake 600w
I can run any game on max settings on a resolution of 1440x900
now youre old pc is pretty good
-CPU:Intel core2duo e4600 2.4Ghz
-VGA:point of view nvidia geforce 9500Gt 512
-RAM:4gig DDR2
and since you have a 9500gt that means youre motherboard can support pci-express cards,
ok how about you just upgrade your old pc?
youre cpu is great for games, youre not gonna notice any difference in gaming, its just that installing games will be faster on a core i5 but trust me its not worth it, and you wont get any +fps in games, me and my friend have tried this on a corei3 vs a dual core and there was no difference in the fps, even if there is there will be only max +5fps.
for you rams, well there good man you dont need ddr3, what you'll notice the difference between a ddr2 and ddr3 is that the loading times are faster on a ddr3, yeah but just 5 seconds faster, again me and my friend have tried this...
trust me man, you dont need to upgrade youre entire case, just buy a new power supply and a vga and you'll be set for another 4 years, and you could possible need a new ups to support youre power supply if the one you have is weak...