i want to buy 512MB PC2700 DDR memory. on this page (http://www.smksuperstore.com/130/listproducts.htm), that memory ranges from $61-$128 depending on the grade. WHAT IS UP WITH THESE GRADES?!!??? if i get the $61 grade would i probably notice anything different between the other grades or have problems?? keep in mind i would not be using it for communicating with the space shuttle.