Re: AMD Opteron
i'm guessing you are talking about the opteron 144(as opposed to the 148, 165, etc.)
AMDs are better for gaming and the opteron offers the best performance for the price.
the 1.8Ghz 144 can be overclocked to about 2.6 on stock cooling and many have been getting to 3 Ghz on water. opterons in general are very good because they are originally server grade processors (which means they undergo more rigorous testing for stability.)
make sure to look around though before you buy, you can usually find a 144 for aroun $140. try monarchcomputer.com, zipzoomfly.com, tankguys.com, and even tigerdirect.com.
just looked and monarch has them for $138 OEM which means you need a HSF and thermal paste but it still might be cheaper. who knows check it out. i was going to get a 144 but decided to just save some more money and go dual core with a 165.
also don't be scared off by AMDs lower Ghz. 3Ghz in an AMD is somewhere around 4.2 Ghz intel. have fun.
So it Goes.