I never used valueram, but for 4 extra dollers you get better quality, comes with a heat spreader, timmings are faster and it looks cool, also it is easier to overclock.
When I looked at Corsair value ram it's usually 3-3-4-8 or 3-4-4-8.
Trust me just get 2x1 it's less risky then getting 4 x 512, and you'll also save 5 bucks on shipping. Also when you use 4 sticks you're forced into 2T timings, instead of 1T.
im gonna stick with 2 1gb sticks, everyone says it will work faster and better with the BIOS, so no 4x512 for me, and i will use the OCZ, definetly better!!!!!!!