Out with the REALLY old (K8)

Since WinXP is expiring, I'm remembering some old builds that will need to be replaced.
In particular, I remember patching together a system for my brother a while back.
It's an old K8 (969) based system, and I found a nifty Opteron 170 for him.

He does music editing w/ a great program called Mixcraft. I can't recommend that enough, it runs on very little resources and he gets amazing results. He is very happy with it, and will be reluctant to change to a new system. He's of the "it ain't broke" mindset... and I get it.

But now I'm wondering how the current gen of CPUs match up to the old. Considering Moore's Law and all that, theoretically a low end CPU should be able to match what the old "enthusiast" chip could do.

Obviously I'm going to upgrade him to a higher performance system. But I'm curious as to what the FLOOR is. What would be the minimum... or the break even point... performance wise.

What is the lowest performing CPU that's available today that would give essentially the same performance as this old K8 Opteron?

For example, how would an A4-6300 stack up? Would this $55 APU hold its own against the once "mighty" Opty 170?  Would it out-perform the old K8? Or would this budget option still fall behind the old server grade dual core?

http://www.cpubenchmark.net/compare.php?cmp[]=517&cmp[]=2083