Need advice on getting/building a new computer

My comptuer is about 5 years old(with a few upgrades)... the lastest game I can play is Warcraft III: TFT. I want to build a new pc in time for Starcraft II(which may hit Q1 or Q2 2009) and Diablo III. I haven't really had much to do with ripping comptuers about for years... so I don't know if I'll be able to build one myself very well, or if I should just get a prebuilt(but it cost more). I want to spend about $1500 total, not including the monitor. As for the monitor, I got this in mind:
http://www.newegg.com/Product/Product.aspx?Item=N82E16824001268

As for the rest... I don't know! I need advice on what to get, I'll spend $1500, or a few hundred extra. I hear things about DDR3.. is that worth getting? I need just a pretty good setup.

Which monitor is better.. the one I have posted, or this one?
http://www.newegg.com/Product/Product.aspx?Item=N82E16824001096

Which monitor is better.. the one I have posted, or this one?
http://www.newegg.com/Product/Product.aspx?Item=N82E16824001096

Kasceis18

The first one and graphics card wise, I forgot to mentioned HD4870x2.