Hi,
I am using x-450 frame of quadcopter with kk2.0 and kk2.1 board .
now i would like to upgrade my quad using GPS controller. i don't want some more expensive controller, just confuse about APM and NAZA m Lite with GPS. which one is better ? or is there any other controller , so please suggest me.

Thank you.

If you prefer plug and play then go for the Naza lite, if you like to tinker and have patience then try the APM.

yeah i want plug and play...   
so naza is better ?

Apm requires a lot of tuning to get the best performance but there are rewards to it. I use the Naza lite because I'm lazy. It is easy to setup and smooth.

Yes, as of now, Naza it is, hands down from beginners point of view.

Alongside try a multiwii board without GPS and if you can tune it, you would have an idea on how APM works. Headfree mode in multiiwii is great for beginners/intermediates.

Thank you sidewinder and ashimda....