mySQl ?

I go to this other forum and they use an apache/ mySQL server and the phpBB forum is quite huge (not as big as here though) and it is a bit sluggish recently. One of the admins had said that he thinks because he doesnt have time to archive the old posts, so mySQL is running slower, or is it the host company? Also would switching to, for instance, a bought database, like Microsoft SQL or Oracle make any difference in speed?

I think switching on gzip in the forum's configuration will help with the speed.

Thanks Sidez =)