Re: modify default

I am not aware of any public extensions like that but if you have some ASP knowledge it shouldn't be that hard to implement. I would suggest looking at the code where categories are listed in default.asp. I would rename "default.asp" into something like "topics.asp" and write a new page like you mentioned as "default.asp".

Just list the categories via links which pass "CategoryID" to the "topics.asp" and "topics.asp" would take care of it, you don't have to change anything on it.

As for the topic count, it might be just a little bit harder since that knowledge is currently not kept in the database (though, you can always write an SQL statement to dynamically calculate the topic count every time the page is loaded).