STYLETHREAD -- LET'S TALK SHOP!

does anybody have experience with the quality of diamond.com or ashford.com?  I want this:

http://www.diamond.com/detail.asp?Sn=369500201&nc=ID3C&pf_id=9244&kit_id=&md_id=&comp=

Has anyone seen something similar for cheaper?  I like the size (1/2"), the chain length (16") and the white gold and diamonds- I dont like the price and I would prefer that the chain attach in the middle of the peace sign on each side.  Is this too expensive or a good price ($579)?  I would wear it often so thats not the problem. I know not very much about diamonds...