About PSUs:
Well, what I did for my build to determine the wattage was first calculate how much wattage I needed. It came to around 475W. Then I changed the video card from 1 to 2, and the wattage went up to 600W. The reason I did this was if I want to SLI/Crossfire my system I'd know how much power I'd need. Keeping the 600W in mind, I got the "cheapest" PSU with the highest wattage, a Raidmax 730W PSU. Now I have the freedom of adding parts without having to worry about my PSU. Nothing wrong with extra wattage at your disposal, even if it's a couple hundred of them! :p
As Queen said, it's not good to buy a cheap PSU, I spent around $50 on mine but many will tell you to spend $100 on a brand like Corsair or Antec. Honestly, I don't think you need one of these brand name ones. Just look at the user rating for whichever PSU you're going to buy. If lots of people are saying it dies on them, do not buy it! If the PSU has a high rating, then I'd say you're safe with it. It's been a year and this PSU is giving me no issues whatsoever. Beware though, there are some real crappy PSU's you don't want to touch.
Here's a 600W Corsair I just found on Tigerdirect.
Here's the PSU I have. Unfortunately I couldn't find it on Tigerdirect. I'm not sure if you can order from Newegg, but I'd highly recommend this PSU!
Honestly I think you'll be fine with the PSU included with the kit. I'd say buy a different one only if you need more wattage.
As for the graphics card, take a look at this this, it'll be worth the extra 20-30 bucks ;). I think the card you're looking at will be a bit "eh."