As well, with an i3 at you it will go very well. 720p is not a very demanding resolution.
I have an Asus laptop with E2-1800 APU and it's going great playing 720p MKV files with an average size of between 3GB to 7GB.
So, with an i3 you must go even better.
One suggestion, make sure you have at least 4GB ram. Preferably 8GB.