The first thing i notice about the choice of knives on ebay is the amount of good stuff verses the bad stuff.
My advice is stick to a reputable brand as buying cheap will usualy lead to disaster.
Stick to a smaller blade as the law hates big knives.
The better companies ie: Shrade pre 2004, Puma, Boker, Buck and many other reputable brands offer a fine edge made of exellent steel.
Why waste time on cheap large knives that are totaly useless.
Be prepared to pay a little more for a knife that will last a lifetime