My vote goes to implementing options 3 and 4. The reason for this is because post count and ranks should in some way reflect a particular users knowledge, somebody who posts all day in General Discussion and spams around the boards is going to get a high posts count but they have no knowledge of the area that this board is aimed at that being computer hardware/software. I much prefer the stars and ranks to a simple post count i.e. 100 posts per star or something and different coloured stars the more you have. Then its always nice to reward helpful and regular members with a senior status to reflect there knowledge in the particular subject. I think you get the gist of what im saying anyway just my 2p
EDIT: Also i vote option 2 a custom avatar is always nice, 500 seems a little on the high side but its reasonable, somebody has to pay the hosting bill, and the less bandwidth used the better
