You can adjust the vibrate/ring here:
How do I edit my notification tones (profiles)? - BlackBerryFAQ
Some ringtones are louder than others, too. Also, by default when you use ring & vibrate together, the device will vibrate THEN ring - it will not do it simultaneously. I seem to remember a 3rd party application that came out recently that would let you do that, though.
EDIT: Found the link:
VibAndRing - Personal Productivity Blackberry Software on MobiHand