[CentOS] NFS filesystem recommendations please (and problems with XFS)

Hello all,

I am implementing a new mail server into our environment consisting of 
three machines - two Dell Opterons that will act as load balanced 
Postfix servers, and a 1.5TB RAID10 NFS server.  All three machines are 
running CentOS 4.5.

Since the NFS is going to be used for only mail, I was kicking around 
the idea to use XFS.  I have CentOS installed on an ext3 partition, and 
with the leftover space on the NFS I created an XFS partition.  I tried 
to implement XFS into the kernel, and was coming across some issues.  
Even after installing xfprogs and xfsprogs-devel, and issuing the command:

yum --enable-plusrepos install kernel

I booted up the kernel and still could not mount my XFS share.  I keep 
getting this error:

mount: fs type xfs not supported by kernel

After googling around (and not finding out how to get XFS enabled in the 
kernel), people had some concerns about using XFS due to issues and it 
being about as fast as ext3. 

Also people said that I might run into issues with XFS if I run 
NFS+lvm+xfs+md but I'm not sure if I run lvm and md and if that applies 
to me.

I found this benchmarking blog someone wrote that compares the speeds in 
Ubuntu with all the filesystems in a Postfix server environment 
(although it's not NFS):

http://piao-tech.blogspot.com/2007/04/file-system-benchmarks-for-postfix-mail.html

With all this said, I'd like to use XFS, if it indeed is going to be the 
fastest for the solution I want to implement.  If you guys can help me 
get that installed by telling me what I need - great!  If you think XFS 
isn't going to work as efficiently and fast as I want it to, and there 
is another filesystem (such as ext3) that will be more stable and just 
as fast in my setup, I'm all ears.

Thanks everyone in advance.

Patrick