Goodness, I hope I'm not too late posting to the thread -

To play harmonica in 2nd postion (i.e. cross harp) and end up in E flat, you'll need an A flat harmonica. After all, an A harp plays blues in E, so it stands to reason that an Ab will play blues in Eb.

Re what harmonicas to use - I played Hohners for years, but about five to ten years ago noticed the reeds started going flat very very quickly. I've switched to Lee Oskars, which last a lot longer, and have the advantage of having replaceable reed plates. (Of course, so do Special 20's and some other Hohners). However, A flats are among the most difficult key harmonicas to locate, so I wouldn't be too picky about what kind it is if you do find one.