Need help getting an audio card and headphones

My current setup is onboard audio with a cheap walmart headset. I'm not an audiophile, so this setup actually works well for me. However, while working on my computer all day, I tend to watch tv shows and movies on my computer. Sometimes I'll listen to music. But I figure I just want a nice upgrade so hopefully work is a little more enjoyable when I'm falling asleep.

For headphones I'm thinking of Grado Prestige Series SR-60i Padded Headphones (http://www.amazon.com/gp/product/B0006DPMU4/ref=ord_car...). It was recommended by several sites for the price range and I think it's probably best for me. Don't want to spend more than $100 on headphones just yet.

But I'm not sure what soundcard to get. I've seen a couple of them with a headphone amp but they are $200. Do I need this powerful of an audio card for a $75 headset watching things I'll only watch once? Or, can I get by with a cheaper audio card? I'd really like to spend $100 or less, but will save up for the better one if it's simply that much better.

And, how do I upgrade it? Should I get the headphones first and wait 2 weeks to buy the card, or buy the card and wait a week to buy the headphones? Or should I just wait 3 weeks to buy the pair?