mini display port to dvi is only $9.75 on www.monoprice.com
And i would shoot for the 6gb of ram since the new Snow Leopard upgrade will definitely take advantage of it when it comes to Adobe products and Final cut.
Spend once and not worry about it later..
You can also look into the miniDisplay-HDMI if you have an HDTV with HDMI so you can do playback on that. Quality is great.