I love learning something new!
This is quite easy with BIS, but it took a bit of digging to find out if and how to do it with BES.
The KB article is here:
How to set up Level 1 Notifications
Basically you want to set up a filter that will set specific emails to Level 1, and then set up your Level 1 notification under Profiles.
You can do this on your BlackBerry. Go to Messages, Click the wheel/menu button and select Options, then select Email Filters. Enter the info there, and make sure it's set to forward to your device, and will set the message as a Level 1 message.
Two notes.
The domain trick noted in the KB article (to use simply @domain.com) for the filter didn't seem to work.
However, you can enter multiple email addresses (don't know what the limit is) separated by a semicolon (;).
You can do the same with BIS filters, but you can use just the email's domain, and even partial email names there.