would getting 8gb of ram be worth the extra cost?
For now, no.
You can do 6GB and keep dual channel capability. get a 2x2GB kit and a 2x1GB kit. You've chosen a triple channel memory kit when AMD systems only do dual channel (hence 4 RAM slots)
You haven't chosen a PSU so I'll recommend this:
http://www.newegg.com/Product/Produ...9005&cm_re=corsair_650-_-17-139-005-_-Product
Not CD/DVD drive to install that copy of Windows?
That's a very nice board, but if you never plan to Crossfire,
(and you certainly won't need to with a HD5850) you can get by much cheaper.
6 Core Phenom is overkill also, but it's personal preference.
If you've got the cash, then build it. :good: