CentOS virt - Aug 2008 - Installing xen from xen srpm compiled rpms

When I use yum to install xen 3.2.0 and xen-libs it also pulls in then centos
kernel-xen?
I thought the srpm contained all that was needed besides obvious deps like
bridge utils etc?

To get this running, I change the grub stanza kernel-xen creates to have the
kernel point
to xen.gz-3.2 and one of the module lines to point to my custom initrd for
pciback loading.
That leaves the other module line kernel-xen wrote for
vmlinuz-2.6.18-92.1.10.el5xen intact.

Why does kernel-xen get pulled in and what's the significance of the vmlinuz
line?

Thanks!
jlc