Memory - stick to a reputable manufacturer such as Crucial (who are very reputable, and available at newegg or direct from www.crucial.com)
HD - you're going to have to read around a bit. Every HD manufacturer has had horror story series of drives... As long as you avoid those particular series, there's not much in it IMO. Go for the cheapest big-name (are there any others??) branded drive in your desired capacity. You might want to consider 5400rpm drives for cost efficiency - seek times are slightly longer, but bandwidth should be comparable.
Vid card...What's the intended use? Office, gaming or AV? Do you require DVI output (ie, do you have/intend to buy a flat panel monitor). This is probably where your greatest additional cost or saving will be made, so decide carefully..
Case/PSU. It's still hard to beat Antec for a case/PSU combination in terms of quality and value. I'd avoid 'no-name' brands, especially for PSUs.