Hashrates for Opteron and Xeon CPUs I'm looking for the benchmarked hashrates of both a 1.0GHz Opteron 2007 CPU, as well as a 1.2GHz Xeon 2007 CPU. I looked here but didn't see them mentioned.

Also, on that references page, I don't see anything mentioned for how the hashrates were computed. What mining app is being used as the benchmarker for all those stats? Thanks in advance!
Although those particular CPUs aren't listed, you can infer from the other CPUs in that table that the hashrate will be only a few Mhash per second. CPU mining isn't cost effective today. (Which is why the list of hash rates for CPUs is fairly out of date.) See also this question about whether CPU mining is worth it.

To answer your follow up from the question comments, it's not entirely clear how ASICs will change mining because the number of ASIC machines shipped has been so limited.  If ASIC vendors could deliver in volume at the promised amounts of GHash, yes, they would probably be the only lucrative way to mine going forward. But all predictions regarding the future of mining have to be taken with a grain of salt: it's always hard to predict the future. The end of GPU mining has been predicted for a couple years now, but the rising exchange rate has been keeping it alive.