So, my girlfriend got me 10.5 for xmas (yes, she's awesome).
I was initially hesitant to pay for the upgrade myself, partially due to the pain I went through to set it up as a server in 10.4, but I'm happy to say that it was WAY easier on 10.5. First of all Apache 2 and PHP5 come pre-installed, and after doing the in-place upgrade (of 10.5) my mysql and svn installs still worked! So all I had to do was configure the default Apache2 to be similar to my old setup, mainly for svn and using port 82 (my isp wont allow me to serve from port 80).