An affordable upgrade if you wish to max out your G34 opteron system, the 6386 is the last and best owner controlled x86 CPU.
http://www.ebay.com/itm/AMD-OPTERON-OS6386YETGGHK-6386-SE-2-8GHz-16MB-L3-Cac... (Note: I am not affiliated with that company)
It is one of the best CPU's on cpubenchmark.