Could someone tell me if this is a decent gaming pc?

I was just wondering if someone could give me some feedback on a possible pc I may be getting. Also ne question, does the type of thermal paste really matter to this machine very much? I can also add more cooling if Needed.

Intel Core i5 Processor i5-2500K 3.3GHz 6MB QUAD CORE

INTEL COPPER HEAVY DUTY LGA 1155/1366/2011 COOLING FAN

MSI H77MA-G43 LGA 1155 Intel H77 HDMI SATA 6Gb/s USB 3.0 Micro ATX Intel Motherboard

8GB (2 x 4GB) 240-Pin DDR3 1333 (PC3 10600) Dual Channel

SEAGATE / WD 1TB 7200 RPM 32MB CACHE SATA 6.0Gb/s

22X DVD-RW DUAL LAYER

ATI RADEON HD 6770 1GB DDR5 2DVI HDMI/Disp-Port CrossFire PCI-EXP Video Card

REALTEK 8-CHANNEL DIGITAL SOUND ONBOARD

REALTEK 10/100/1000 Gigabit Network Card (onboard)

APEVIA X-Plorer2 Case w/ Side Window-Black

1x OKIA HEAVY DUTY CASE FAN

hec X ORION 585 WATT POWER SUPPLY (MEDIUM)