If you're going to be doing alot of overhead casting, the switch is a better choice than the spey, I find my Beulah 7/8 is much easier to cast in that regard, and I've had it out tossing big bull trout streamers both overhead and spey casting with no problems so far.
For lighter duties, talk to the guy selling the 4/5:
http://flyfishcalgary.com/board/index.php?showtopic=3659
Beulah recommends either a 6 or 7 weight line with it, depending on the taper.