Sibername is a trustworthy domain registrar and you are able to use them with no doubts.
They have provided their services for a long while and prices on them are reasonable.

I have found the following specials on sibername domain name registration services:
.CA Domains $13.45
.COM Domains $13.45
.NET Domains $9.95.
What do you think of their prices?

See, if they can provide you domain registration as an addon service at no extra cost. If they can then try to research about the companys web hosting services, because it is better to host and register domain at one place for better support.

Guess the idea of domain registration with sibername.com seems amazing for me.
.CO is possible to reg with them at a modest rate.
Services are stable from them and their privacy policy is free of charge.

While I agree with the principle Samlisa, I have to say, please not Godaddy, I'm never keen on people going to other domain registrars but Godaddy are awful!

I know only nice things about sibername domain registration services.
Specials are web master-friendly and they work with no glitches.