I think you are in the right place...
From my point of view ISPConfig
is excellent , i don't know if you gave it a try or not,but if not you should.
I used ISPConfig 2.xx for years and it works fine and i plan to switch to next major version (3) in days.
May be our requirements different,but when i searched for a the best open source control panel, ISPConfig deserve to be it. Every one from the others seems to be incomplete project, leaks some functions , not well-organized or has not enough support.
At last i did't see any Open source CP has huge and active support website like ISPConfig which is supported by this webits.