What kind of monitor do you have right now? I would get a better computer first and then go too a thrift shop or somewhere and buy a cheaper, better monitor.
Any 939 mobo will run opterons, the trick though is that they dont support them (unless they say they do). This means that if you burn out you mobo or cpu, you have voided the warranty. Its a risk you'll have too take if you want too get the most of OC'ing.