Is this pc good or should I change some things?

Here's a better build.

PCPartPicker part list / Price breakdown by merchant

CPU: AMD FX-8320 3.5GHz 8-Core Processor ($149.98 @ OutletPC)
Motherboard: ASRock 990FX Extreme3 ATX AM3+/AM3 Motherboard ($99.99 @ Newegg)
Memory: Team Xtreem Dark Series 8GB (2 x 4GB) DDR3-1600 Memory ($72.99 @ Newegg)
Storage: Western Digital WD Green 1TB 3.5" 5400RPM Internal Hard Drive
Video Card: Sapphire Radeon R9 280X 3GB Dual-X Video Card ($239.99 @ Newegg)
Case: Cooler Master Elite 430 ATX Mid Tower Case ($27.99 @ Newegg)
Power Supply: Corsair Builder 600W 80+ Bronze Certified ATX Power Supply ($34.99 @ Newegg)
Optical Drive: Lite-On iHAS124-14 DVD/CD Writer ($13.99 @ Newegg)
Total: $639.92
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-08-13 14:24 EDT-0400

-Same CPU as before, but now with a motherboard you can OC on.
-Cheaper kit of RAM
-R9 290X. WAY more powerful than the GTX 750Ti.
-Cheaper case (so you can stay under $650 and still get a R9 280X)

As a future upgrade I would get a 7200RPM hard drive OR an SSD, and a aftermarket CPU cooler.
 
Solution
Get a better PSU and motherboard, especially if you're going to be overclocking...

PCPartPicker part list / Price breakdown by merchant

CPU: AMD FX-8320 3.5GHz 8-Core Processor ($149.98 @ OutletPC)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.99 @ Micro Center)
Motherboard: MSI 970 GAMING ATX AM3+ Motherboard ($99.99 @ Newegg)
Memory: Team Xtreem Dark Series 8GB (2 x 4GB) DDR3-1600 Memory ($72.99 @ Newegg)
Storage: Western Digital WD Green 1TB 3.5" 5400RPM Internal Hard Drive
Video Card: Sapphire Radeon R9 270X 2GB Dual-X Video Card ($174.80 @ Newegg)
Case: Cougar Solution (Black) ATX Mid Tower Case ($37.99 @ Mwave)
Power Supply: SeaSonic S12II 620W 80+ Bronze Certified ATX Power Supply ($70.98 @ Newegg)
Optical Drive: Lite-On iHAS124-14 DVD/CD Writer ($13.99 @ Newegg)
Total: $650.71