since you already have the mobo: fx 8120 + cm hyper 212 evo cooler or something like noctua nh d14.
if you want to wait till piledriver has come out, then fx 4100 or ph ii x4 960T.
if you decide to get a pd cpu later, the 6-8 core ones might seem like sidegrades.
you can check out this link:http://www.frostytech.com/top5heatsinks.cfm#AMDHEATSINK
video editing softwares love cpu cores and ram, 8-16 gb ddr3 1600 should be starting point.