N560 looks great - I am amazed this has totally passed me by
I can't find any price below £300 though, Ebay or elsewhere.
How good is the GPS? Have you run any mapping applications on it e.g. Oziexplorer?
Does WM5 run old software e.g. stuff written pre-wm2003? Most of the nice aviation apps for W&B etc are quite old.
Have you tried it with a 4GB or 8GB SD card? Most things don't work with a > 2GB SD card.