I made another benchmark test, by ripping a CD to MP3.
I used Incognito's latest album "Eleven", CDex ripper with quality=2 (high) and 256 kbps setting.
P4 2.26 GHz: 08:26 minutes.
AMD Athlon 64 X2, dual core 4200+: 02:55 minutes.
For ripping the new computer is 2.9 times faster. I'm quite happy about that.