Looking to buy a gaming computer for around $600-700, and narrowed it down to these two.

iBUYPOWER Gamer Power 535SLC
-AMD Athlon II X4 620(2.6GHz) 64 bit Quad-Core Processor
-4GB DDR3 1600 of Memory
-500GB SATA II Hard Drive
-ATI Radeon HD5670 1GB graphics card
-480W Power Supply
-$619.99

(Additional Information here.)

or

CyberpowerPC Gamer Ultra 2023
-AMD Phenom II X2 550(3.1GHz) 64 bit Dual Core Processor
-4GB (2x2GB) DDR3 1333 of Memory
-500GB SATA-II 3.0Gb/s 7200RPM HDD Hard Drive
-NVIDIA GeForce GTS 250 1GB PCI Express Video Card
-700W Power Supply
-$659.99

According to some reviews, this computer tends to crash often.

(Additional Information here.)

I'm not a "hardcore" gamer, so I wouldn't need to run games like Crysis, etc., just some modern games like L4D2.

I'm leaning more towards the first one due to fear of crashing, lower price, and the Quad-core, but this is my first gaming computer so any advice would be helpful.