This is much higher quality than a Xclio. The Xclio's real power is probably somewhere around 400w and it's not very efficient.
The 500w Antec is more than enough. If you decide you want to upgrade that video card to something like a GTX580, you should go with something a bit more powerful like this:http://www.newegg.com/Product/Product.aspx?Item=N82E16817151096
Seasonic is very high quality.