CentOS 4.x would be my choice for now, as it's my mainstay OS (where RHEL's cost isn't justified) on just about everything else I manage, save some Xen setups (including KnifeRights.org) that require something newer. If it wasn't for the small smattering of ASP used on other portions of the site, I'd have them ported over already as part of the new server. In fact, the first iteration of the "new" server was CentOS 4.4 until I discovered the reliance on ASP code w/o any real path to porting it to something LAMP friendly (or spending $$$ on ChiliSoft ASP).

Hope this helps, and sorry for geeking out the Survival forum <img src="/images/graemlins/grin.gif" alt="" />