Can anyone suggest a plugin for register

I have been searched for days. I need a one that I can

1.check if the username exist;
2.set criteria for username and password;
3.remind the new user as he enters the info;
4.setup the nickname and use it as default;
5.set password when first reg;
6.optionally send email for confirmation.

Please let me know if you have any suggestions.

Thanks in advance.