Don't know about Buddypress as i've never used it. I have just started a project using DirectoryPress simply because i couldn't find a decent directory plugin.
You can create child themes with Directorypress. To modify the ouput of various elements you can copy the element to your child and then modify it (header, single etc). It also has some hooks and filters you can make use of to modify stuff.
Getting help on the forum is a little hit & miss in my experience. Not wanting to put them down, but i've been spoiled here and was expecting a little more in terms of support - plus you won't find code snippets or examples like you do with Genesis.
Most of the options are in the admin area and most parts of the setup include videos to watch, so it's pretty good in that respect - but it is going to take a few hours to watch the vids and get your head around the system.
Hope that helps a little.