I have not ever heard about the file managers you mentioned before.
Well, actually I have found using a file manager with some desktop environments on Unix/Linux more versatile compared with the Windows Explorer. I think it's just you have not been introduced a really good one yet.
I recommend you try Konqueror yourself - you'll probably forget 4pane ever since. It does not quite restrict the number of split views created (of course, your screen resolution and size restricts you!), and you can split both horizontally and vertically in any way that makes sense to you. Also, because Konqueror is a Web browser, you can have a pane that is browsing a Web site, while the other pane viewing files on your disk. One thing I like it best is its multi-protocol support (using what they called KIO-slave). Apart from browsing local filesystem, you can browse remote filesystems over FTP, SSH, Samba etc. in a pane and edit files as if on a local filesystem, and browse ZIP/TAR archives as if they are extracted.
Some (old) screenshots are available here:
Konqueror - Konqueror - Web Browser, File Manager - and more!
Konqueror is the default Web browser and file manager for KDE (up to v3) so all distributions having KDE in the package list must have it. You can still use it in KDE4 (but a bit crippled in comparison in my opinion) if you get hold of it. I have made a screen capture on KDE4.
Someone says Krusader is a better file manager than Konqueror, but I cannot quite see why myself.