I don't think you should get that Antec SmartPower 500W !!!
Let me tell you a short story.
Just recently, I was also shopping for another power supply for my PC. The Antec Smartpower 500W was the choice that was on the top of my list. But, like all the things I buy, I do some research (Google) on the product first.
The professional reviews on the google results were all good, but they were all dated before 2005. Then, I just added the word "bad" to my google search, and it came up with many pages of people saying how Antec's smartpower line is not good anymore.
Just look at the newegg user reviews for them. They all start getting negative feedback at around early 2006. They all say that this unit lasts under a year.
There seems to be a bad batch out of the factory. After more research at that point, it seems that Antec's contract with CWT has expired, therefore having no access to good capacitors.
In the end I got another power supply (not the Antec SP 500) because I can't be bothered to RMA one to Antec every six months.
Antec is still very reputable for good power supplies but I strongly suggest you stay away from the SmartPower line for now.
The rest of it looks good.
Good luck with your computer and merry Christmas