Really it depends on what you want to do. You are asking about 2 very different platforms - read motherboard.
If you put the amd 5200+ on a mobo w a 790GX chipset such as:
GA-MA790GP-DS4H
here:
http://www.gigabyte.com.tw/Products/Motherboard/Products_Overview.aspx?ProductID=2887
then you will have a platform that you can use and enjoy now;
plus
an ez upgrade path to soon to be released PhenomII cpu - since the AM2+ mobo will support it with a mere bios upgrade.
So I see it as a temporary cpu. Both cpu's mentioned are getting old.
But I don't know details of your rig or your intent. However, that's the path I would follow. See features on link above.