I need big help from community

I know out there are a lot of system configurations already but unfortunately i can not afford smth over 500-550euro maxim.
I am on internet club right now and i am reading every day tomshardware forum bcz this time i dont want to fail with a homebuilt system.
Till now this is what i built


PU AMD Phenom II X4 965 3.4GHz Socket AM3 125W Deneb Black Edition Boxed HDZ965FBGMBOX
RAM DDR3 Corsair Vengeance CMZ8GX3M2A1600C9 1600MHz 8GB (2x4GB) CL9 ( ON MOTHERBOARD ASROCK OFFICIAL SITE AT COMPATIBILITY SAYS AT 2X4GB KINGSTONE the blue one ) i think dosent matter if is kingstone or other company no ?
Scheda Madre Asrock 990FX Extreme3 Socket AM3+ DDR3 SATA3 USB3 ATX
VGA Asus ENGTX550 TI/DI/1GD5 NVIDIA GeForce GTX 550 Core 900MHz Memory GDDR5 4104MHz 1GB VGA DVI HDMI HDCP ( I CHOOSED THIS BCZ IS PCI-E 2.0 , THE ONE WHICH MY MOTHERBOARD FX990 EXTREME3 SUPPORT )
Hard Disk Interno 3.5" Western Digital Caviar Black WD5003AZEX 500GB 7200RPM 64MB SATA3
ANTEC VCG 520 PSU
ANTEC 300 CASE


this is my 500 EURO PC SYSTEM made till now


Now why i am asking for help ? bcz i am still an amateur and i want to be sure i wont fail this time like i already did with my other PC   i see a lot of things like for example ( SSD system disc ) and so on ....


I want to mention that i am not looking strictly for AMD , ill rather choose INTEL but my knowledge about INTEL is even poor than AMD so thats why i want a good advice from experts.


SO please share with me a good HOMEBUILT PC DEKSTOP INTEL or AMD which will bring me a good perfformance for gaming/casual using at a good price ( minim 400 euro maxim 500-550euro )


Dont hesitate to post some combos which maybe will cost a little higher than 550 but the difference can be bigger , i will take into account all suggestions that i will recive


sry for my english and i cant wait to come in 1-2 days back to internet club to see which will be my next PC