Arjaan :
it is a Thermaltake w0134ru 550w
So you are definitely going to want a new PSU aswelll.
Heres a couple of upgrade options assuming you can use your current case HDD and optical drive.
Option 1
PCPartPicker part list:
http://pcpartpicker.com/p/1Ttdc
Price breakdown by merchant: http://pcpartpicker.com/p/1Ttdc/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1Ttdc/benchmarks/
CPU: AMD FX-8350 4.0GHz 8-Core Processor ($184.99 @ NCIX US)
Motherboard: MSI 990FXA-GD65V2 ATX AM3+ Motherboard ($138.99 @ Mwave)
Memory: G.Skill Sniper Series 8GB (2 x 4GB) DDR3-1866 Memory ($73.98 @ NCIX US)
Video Card: MSI Radeon R9 270X 2GB Video Card ($219.99 @ NCIX US)
Power Supply: XFX 650W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($69.99 @ NCIX US)
Total: $687.94
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-10-26 14:28 EDT-0400)
Option 2
PCPartPicker part list:
http://pcpartpicker.com/p/1Tti9
Price breakdown by merchant: http://pcpartpicker.com/p/1Tti9/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1Tti9/benchmarks/
CPU: Intel Core i5-4670K 3.4GHz Quad-Core Processor ($219.99 @ Newegg)
Motherboard: Asus Z87-A ATX LGA1150 Motherboard ($134.99 @ NCIX US)
Memory: G.Skill Sniper Series 8GB (2 x 4GB) DDR3-1866 Memory ($73.98 @ NCIX US)
Video Card: MSI Radeon R9 270X 2GB Video Card ($205.66 @ Newegg)
Power Supply: XFX 650W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($69.99 @ NCIX US)
Total: $704.61
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-10-26 14:31 EDT-0400)
Option 3
PCPartPicker part list:
http://pcpartpicker.com/p/1TtjR
Price breakdown by merchant: http://pcpartpicker.com/p/1TtjR/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1TtjR/benchmarks/
CPU: Intel Core i5-4430 3.0GHz Quad-Core Processor ($189.99 @ Newegg)
Motherboard: Asus Z87-A ATX LGA1150 Motherboard ($134.99 @ NCIX US)
Memory: G.Skill Sniper Series 8GB (2 x 4GB) DDR3-1866 Memory ($76.99 @ Newegg)
Video Card: EVGA GeForce GTX 760 2GB Video Card ($249.99 @ Amazon)
Power Supply: XFX 650W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($69.99 @ NCIX US)
Total: $706.95
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-10-26 14:33 EDT-0400)
For options 1 and 2 you could upgrade the stock cooler to a better aftermarket cooler and OC the CPU.