The best way to futureproof this rig would be to get 2x2gb sticks, as a major forseeable upgrade in a year or 2 would be 8gb of memory. I think if it was me, and I had to choose between 4x1gb cl5 memory, or 2x2gb cl6 mem, I'd go with the cl6 stuff. I mean, you're going to have to slack timings...