Thinking about a big lizard.

[qiksilver]

Hmm big isnt allways good. Well if you do want something big heres what I think are suited in your case.
Nile,croc,asian water,sulfer water,black throat.
If you have some experience with monitors get one of the first 2 if not get the black throat!

and no, none of the animals you listed are suitable for a beginner.