Your displays are going to limit you a little.
Keep using HDMI to HDMI from the GPU to your main screen.
this is where the limitation is for your second screen.
Displayport carries video and sound but the sound is transmitted slightly differently to HDMI sound.
Your best option for video is GPU Displayport to TV HDMI but, that will not carry sound. Any other combination will give lower video quality and still no sound. You can still get sound to the TV by using an Audio cable. See link.
So you will need the following.
Choose the length of cable from this page, > http://mycablemart.c...AWG Gold Plated
A Displayport to HDMI adaptor. > <a href="http://mycablemart.c...5</a><div>There
are some very good help pages on the site. > http://mycablemart.c...lp/pc_to_tv.php
You could try the new HDMI cable to your main screen to see if it gives a little better performance than the one you are using.