I full heartily agree with Tomas about wasting time talking about Amizilla - it was a noble effort by Bill P but really not feasable.
You're right, porting Gecko is a huge project. But you're wrong about it being unfeasable. Big strides have been taken - just look at the recent activity on the mailing list - Jeff Shepherd is beavering away at it. NSPR (the underlying portability layer) nearly done. Once thats done, I believe the plan is to create a test version that uses an X server for its output. Then I believe that an Amiga native port of the widgets and GFX will commence.
KHTML is quite a big project too, and I would dearly love to see both of these engines on the Amiga. If only I could write a bit more than very simple PHP stuff :-(