Upgrading from 3.1 to 4.0 and wondering about the CMS database (SQL) I/O changes

We are about to install bobj 4.0 sp 6 and was just going to spec out the SQL server the same as the one running 3.1 as the size is very small and the I/O is basically nothing, BUT I was reading on a couple forums that the I/O on the SQL box has changed dramatically with the new version. Does anyone have any experience with this, or know if this is correct? I am guessing that this is really not the case, but do not know and was hoping to get a good idea before I spin up the SQL server to make sure I don't need more than the old

Thanks,

Brian