IMO, RAM really only comes into major play when you're choosing your OS. Vista is a hog, and I wouldn't recommend it. XP Pro is the way to go.
Vista needs about 4GB's of RAM to run properly and at its intended level.
But, first things first.
From what I've read and heard, the i7's are fantastic processors.
As far as GFX cards, I recently bought an EVGA nVidia 9500 GT series 1GB GFX card, and am really impressed with it. All told, I spend about $80 on newegg. (including S&H) If I had the money, I would have bought two so I could run a dual system.