2nd hand PC, what's it worth and will it be able to play games?

[Extern]

My laptop is failing me and I finally have space for a desktop. I would like to play games like the new COD and CS:GO on at least medium at 1600x900, maybe 1080p in the future.

A friend is getting a new system and offered to sell his old system to me:
Processor: Intel i5 2500K / 3.3Ghz
GPU: XFX Radeon HD 7950 Black Edition
RAM: Corsair Vengeance 2x4GB DDR3
Motherboard: Gigabyte GA-Z77M-D3H
Case: Cooler Master CM 690 II Advanced Midtower
Power supply: XFX Core Edition PRO550W

Will this do the trick and if so, what do you think it's worth?

Edit: got a second offer as well:

Case: BitFenix Prodigy
Motherboard: H87I-plus
CPU: Intel Core i5 4440 @ 3.1GHz
GPU: HIS R9 280X iPower IceQ X² Turbo Boost Clock 3GB GDDR5
Memory: 8Gb DDR3 1600MHz (2x4GB) Kingston HyperX
Samsung SSD 840 EVO 120 Gb
WD HDD 500GB
Power supply: Corsair CX750M (750 Watt)

What would this second offer be worth?

 

[superninja12]

its a good system 200-250 is a nice offer