[snakes1100]

Hello
You shoudln't have any issue importing a mysql 4.1.xx database into mysql 5.0.xx version.

The php version shouldn't effect anything as well, unless there is some very old php4 coding in them, so you should be ok in this area as well.

As for a php cache mechanism, any should be fine, but the advantage goes to APC here for per site settings, limiting what domain can use it etc.

I've not found any "huge" advantage to running any select version of apache, so again this shouldn't really matter, but i would run the latest 2.2.xx version, as 1.3.xx is EOL anyways, might as well stay ahead of the game.