Ive seen decent reviews on both but I havent seen a review comparing
them to one another. Ive got the 640 and it sounds OK for a small sub
+ plastic satellite speaker with a full range small driver in it.
I think I saw the 530 at Compusa recently for $59 so Id get the newer
530 since they are newer and look cooler. I got my 640s a while ago
for $49.