Building a possible gaming PC?

Im building a pc that i thinking of just playing games on......i bought a decent computer case, 8gb memory, a Intel BX80571E6800 Pentium Dual-Core E6800 Processor - 3.33GHz, Socket 775, 2MB Cache, 1066MHz FSB, Wolfdale, Dual Core, Retail CPU w/ Fan (I69-6800) to go along with a 320 gb drive, a 400w PSU, a GIGABYTE GA-G41M-Combo LGA 775 Intel G41 Micro ATX Intel Motherboard, ATI Radeon 5450 512MB graphics card and Windows 7 HP 64 bit.........just wondering if this project would be a good gaming PC or would i have to get a bigger wattage PSU and/or better graphics card??.....or can i just go with the integrated graphics provided on the motherboard??