GPU; defiantly stick with the R9 270, best card out there for the price.
CPU; For gaming an i5 4570 would be your best intel Quad core processor, which will perform extremely well in current games.
CPU cooler; Cooler master Hyper 212 EVO, Best in it's price range.
PSU is fine, though I would not attempt to overclock anything due to limited watt headroom.
Total, Not too sure but it should close to budget, if under, maybe consider a i5 4670.