You already have the top i5 CPU and frankly going for an i7 isn't going to help much (if at all) in games unless you get an 875K (for the unlocked multiplier). I'd suggest to get an aftermarket heatsink, the CM Hyper 212 is a popular choice, just make sure to see if it would fit in your case (it doesn't in mine). If you aren't against watercooling you could get by with an H40 even with a slight overclock on your CPU.
For the GPU, if you don't mind buying used stuff you could snatch an HD6950 pretty cheap, around $150+shipping (I got mine used for $120 because the fans broke but I managed to "fix" it
). If you got the money, the HD7850 has one of the best bang-for-the-buck ratios. If you can spend $300 go for the GTX660.
And for storage, I assume those 660GB of yours are constraining you, isn't it? Get a 2TB drive, costs just a fraction more of what 1TB drives go for.
EDIT: forget those prices, I see you're in the Philippines.