I think that almost any distro is equally good if you know what you are doing. Currently I use mandrake 8.1 for a testing server/workstation and redhat 7.1 for a server.
I have used XFS, JFS, EXT3 and ReiserFS. Rieser and XFS are the most mature. XFS is the biggest patch (300K or something). XFS is supposedily the best with large files and Reiser with small. JFS is excellent, and fast, but has had a couple of bugs, EXT3 I wouldn't rely on as of yet - But I have a feeling that is the fs that will ship with Redhat 7.2 (it is included in the beta).
1) upgrade to 2.4.10 kernel - fixes some VM stuff. It is now available from www.kernel.org. Not to many problems on the mailing list - but is still "Beta Stable"
2) Better scheduling (for the lots processes that ACS may create)
look at the schedule patch from http://lse.sourceforge.net/scheduling/
or HPs nice scheduling patch (The industry's best)
3) bounce-buffer elimination for IO devices
For a lot of disk IO, you want to look at the progress of the bounce-buffer elimination for IO devices, like my Fibre Channel adapter.