I just played a bit with the xfe file manager. It might be a good replacement for pcmanfm. It's a long time since I've worked under Windows but xfe reminds me a bit of total commander.

However, there's a small bug in xfe when running on openbox: It somehow doesn't correctly read the openbox desktop borders which leads to the problem that the window is misplaced and the window decoration bar is above the upper screen edge.
That can be solved by checking the option "remember position" in the xfe preferences (that dialogue will also be misplaced) and maximizing the xfe window before closing it.
To maximize it I called this wmctrl command:It gave me 5 seconds time to switch to the xfe window, moved it to a position where I could reach the window buttons and I pressed the maximize button.
From now on the xfe main window should be correctly placed.

While you're at it take the chance to adapt the rest of the xfe options. For example one-click open is a very nice feature on a stylus device and you might want to change some associations of file types with applications. For example I neither like the image viewer nor the text editor that comes with xfe. Therefore I changed those associations to geeqie and leafpad.