My PSU is by Silverstone.
Silverstone makes excellent PSUs. You may actually be fine with the one you currently have. The Radeon 5850 is decent on power consumption.
Anyone know what is the difference between Gigabyte P55A-UD3 and Gigabyte P55A-UD3R?
http://www.gigabyte.us/Products/Motherboard/Products_Spec.aspx?ClassValue=http://forums.bethsoft.com/index.php?/topic/1079401-the-community-tech-thread-86/Motherboard&ProductID=3254&ProductName=GA-P55A-UD3
http://www.gigabyte.us/Products/Motherboard/Products_Spec.aspx?ClassValue=http://forums.bethsoft.com/index.php?/topic/1079401-the-community-tech-thread-86/Motherboard&ProductID=3163&ProductName=GA-P55-UD3R
Extra PCI slots, one less PCI-E x1 slot, extra USB and SATA 3.0 Gb/s ports, eSATA ports...nothing much to rave about really.