It's the ones at the end of the run that are Quite Valuable now. Lungbarrow, The Dying Days, So Vile A Sin, especially. I don't know what they're worth now, but when I was collecting the NAs a few years ago they were going for about £50 each on E-bay, with So Vile A Sin occasionally topping £100. Hence why I do not own So Vile A Sin.