No-one has asked the question - How old is your CX2? You say you have owned it for about a week?

If so, your Motors shouldn't be defective after just this short time!
Have you checked all the usual places for Binding, that could be causing loss of power?

I recently experienced reduced flight times, and blamed either the Motors or Batteries!
Turned out the Outer Shaft was bent, causing binding also on the inner shaft, and draining the battery in no time!

Worth the inspection, and could save you some $$ !
Anyhow, I'd recommend the Xtreme 180 motors if you do decide to "upgrade".

Cheers.