Hi Neal
Although I have bought and used a couple video cards in the past I wouldn't call myself an expert because, like you, I don't play games but I do watch YouTube and TV catchup videos.
The only thing I can advise is that you check out the range of ATI video cards, here is a US link that may help:
Amazon.com: All ATI Graphics Cards - ATI Technologies
I have used a pre-installed 64MB ATI card, replaced it a 128MB card when the original failed, and bought a 256MB ATI card, which I gave away.
Saying that, my primary usage was, and still is, text and word processing based.
Hope you can select the video card you require.
UK Bob