Easa Yahiya :
Thank you for the quick answer
#But the case and RAM is unavailable currently on newegg (P.S. i live in India and only newegg ships to my country) can you suggest another case and RAM similar to these ones?
# the SSD is too expensive. Can you suggest a hard drive instead
#Please correct me in this, but isn't the factory cooler enough?
Ah, I didn't realize that you were outside the US. The cooling fan is because the case is so small that the standard fan won't fit. Changing it so that everything is from NewEgg and using a 500GB hard drive (laptop drive, to fit better in the small case) gives this set up:
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Pentium G3258 3.2GHz Dual-Core Processor ($69.99 @ Newegg)
CPU Cooler: Noctua NH-L9i 57.5 CFM CPU Cooler ($44.99 @ Newegg)
Motherboard: Biostar Hi-Fi B85N 3D Mini ITX LGA1150 Motherboard ($69.99 @ Newegg)
Memory: G.Skill Ares Series 8GB (2 x 4GB) DDR3-1600 Memory ($69.99 @ Newegg)
Storage: Western Digital BLACK SERIES 500GB 2.5" 7200RPM Internal Hard Drive ($54.99 @ Newegg)
Video Card: EVGA GeForce GTX 750 Ti 2GB Video Card ($130.98 @ Newegg)
Case: Cooler Master Elite 110 Mini ITX Tower Case ($39.99 @ Newegg)
Power Supply: SeaSonic Platinum 400W 80+ Platinum Certified Fully-Modular ATX Power Supply ($99.99 @ Newegg)
Wireless Network Adapter: Edimax EW-7811UTC 802.11a/b/g/n/ac USB 2.0 Wi-Fi Adapter ($22.99 @ Newegg)
Total: $592.90
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-01-10 07:14 EST-0500
I changed the RAM, but the case is showing as available right now (they don't have many, so they go in and out of stock frequently).
The PSU that I listed is fanless, so it makes no noise at all. You do pay a bit more for that, but it means that the system makes only a little more noise than an XBox One.
Also, please note that I have not tried out that wifi adapter on the Steam OS - you may have to use command line Linux (Steam OS) to load its drivers - the one that I originally posted has built in support on Linux and Steam OS.
If cost is your biggest concern, the lowest priced power supply from NewEgg that I would use on that system is the Rosewill ARC M450 for $40 with the current promotion code. It is partially modular, so fitting everything in the small case is still possible - but it does have a fan and is not as efficient, so it will be noticeably loud in a living room.