For transaction based hosting, such as databases, we have some dual 64 bit 3.xeons. For most hosting this is some what over the top. We also run some 3.0 P4s that provide more than enough power for most hosting except, video, mp3 and very large data bases.
Often times more memory is more important than processor speed.
On anything but the dual xeons we have 1 Gb on all servers. On the dual xeons we have anywhere from 1.5 to 4 Gb depending on the the servers use but 2 Gb is our standard.