Hi. I too have been looking about for a good File manager. And short of finding MyFTP (which is VERY basic and doesnt do half the stuff you need) I gave up and wrote a simple wrapper for eXtplorer.
I have broken the install down into 2 stages.
Stage 1:
Create a new directory in the root of your Website called "wp-extplorer".
Unzip the content of the eXtplorer Zip into the new director.
Stage 2:
Click Here to download my Plugin.
Login to your WP-Admin page
Click "Plugins -> Add New -> Upload"
Browse to where you downloaded my Plugin, select it, and click "install Now"
Once installed, activate it.
Now click on "Tools" and there is a new menu entry called "eXtplorer". Click on that and your away.
Default username:password is "admin:admin". Change this as soon as you can.
I'll improve it later so the installation is smother and simpler, but for now it does the job.
Hope this is of some help to someone! I'll develop on it some more when I have the time.