This machine is finally dying after many years, so I've decided to build myself a new gaming rig. Well, I say gaming, but my budget will probably be around £700-£750, as well as stuff like disk drives and whatnot. I'm not going for a ridiculously powerful rig, just one that'll be able to handle the new games at good settings. This is my first time making a computer and I could really do with some help. Here's what I've pieced together so far, but I've been told it's not that good. Any advice would be great, cheers. 
-Intel Core i5 660 3.33GHz Socket 1156 4MB L3 Cache Retail Box Processor
-Casecom 6788 Black Mid Tower Case with Full Black Interior/Exterior 120mm Blue LED Front Fan - No PSU
-Western Digital WD5000AAKS 500GB SATAII 7200RPM 16MB Cache - OEM Caviar Blue
-ASUS P7H55-M H55 Socket 1156 VGA HDMI Out 8 Channel Audio MATX Motherboard
-Kingston 4GB (2x2GB) DDR3 1600MHz HyperX Memory Kit CL9(9-9-9-27) 1.7 - 1.9V
-Corsair 650W TX Series PSU - 120mm Fan, 80+% Efficiency, Single +12V Rail
-XFX ATI Radeon HD 4870 1024MB GDDR5 PCI-Express Graphic
(not a complete rig obviously, just the key parts)

-Intel Core i5 660 3.33GHz Socket 1156 4MB L3 Cache Retail Box Processor
-Casecom 6788 Black Mid Tower Case with Full Black Interior/Exterior 120mm Blue LED Front Fan - No PSU
-Western Digital WD5000AAKS 500GB SATAII 7200RPM 16MB Cache - OEM Caviar Blue
-ASUS P7H55-M H55 Socket 1156 VGA HDMI Out 8 Channel Audio MATX Motherboard
-Kingston 4GB (2x2GB) DDR3 1600MHz HyperX Memory Kit CL9(9-9-9-27) 1.7 - 1.9V
-Corsair 650W TX Series PSU - 120mm Fan, 80+% Efficiency, Single +12V Rail
-XFX ATI Radeon HD 4870 1024MB GDDR5 PCI-Express Graphic
(not a complete rig obviously, just the key parts)