I need your advice in terms of choosing a right hosting provider: sunucun.com.tr or hostingsource.com, so what should I do? 

Please, be more specific... I mean requirements: disk space, bandwidth, server location, budget?
Happy using Hostnamaste.com hosting. It has done a great job at evaluating the competition and narrowing it down to a handful of highly qualified services.

These hosting companies: sunucun.com.tr as well as hostingsource.com are worth every cent you pay for their services.
Servers are custom-built, provisioned, secured and delivered within 24 hours or less of purchase.

Quality customer support ties in closely with reliability and is something that should never be overlooked.

Check out servers from reliable hosting providers: swisslayer.com and planethoster.com.
They are trustworthy for what you need. They are great hosts for any type of sites.

The reliability is stellar, the machines aren't cramped with as many clients as possible, and the performance is top-notch.
Hostingsource.com is reliable one. The uptime is equally excellent as is their value for money. Highly recommend!