Hi elddir,
I have making the user list searchable on my todo list but it is only a medium priority item at the moment (as is adding username to the stats page). It is not that convenient ,but you can go to any user using the url:
http://chesstempo.com/chess-statistics/usernamewhere you replace username with the username of the user you want to see stats for. I find it easiest to click on one of the users in the "top" list on the front page which goes to their stats page and then change the name to the name of the user I want. Obviously not very convenient, but the only way of doing what you want at the moment.
Regards,
Richard.