Video card for running my HDTV

I have a computer that is used for driving my LCD HDTV (Vizio M550SV)M550SV | VIZIO. The computer is built on a Gigabyte GA-E350N-USB3 motherboard GIGABYTE - Motherboard - BGA FT1 - GA-E350N-USB3 (rev. 1.0). It uses an AMD E-350 APU and has a built-in AMD Radeon HD 6310 graphics core. There is 8GB of memory added to the MB (2x4GB). This unit has W-7 Ultimate x 64 as the OS.
I have currently a ATI Radeon HD 4550 PCIe card installed on the MB and use it as I initially believed that the picture was improved with it over the built-in 6310. What I am wondering is, shouldn’t the 6310 provide better graphics than the 4450 or is it that the integrated 6310 is restricted by its configuration and maybe the 4450 has an advantage by being an add-on card?
Also, would a newer card help improve the graphics or have I hit the ceiling with the E-350 APU? I only use this computer for watching Blu-rays on the HDTV and do NO gaming. Curiosity is the reason for my questions as there is really no complaint of what I have now.
Thanks in advance..

The HD 6310 only wins when it comes to DirectX version. You shouldn't have any problems with the Radeon HD 4550

Agreed. The 4550 is a respectable little card. It should be fine for movie watching.

You should consider getting a better card, an nVidia, something in the 700 series, a 760 or better.

A good card should always be better then using the cpu graphics.