Thanks all for the recommendations!
Allivymar, I'm sure the filter has a defect causing the vibration. The fish store recommended 'banging on it a bit' to knock a loose fit into place
lol I bet your couch is the perfect viewing spot!
, have you had any clogging that grigg's was saying could happen? how often do you maintenance the magnum 350 and what's involved? What's the setup like, meaning how do the hose(s) secure to the tank, how far in are they submerged, etc? (sorry for all the questions...I haven't found a good source yet showing a canister actually set up. Any links would be much appreciated!)
RG, is your XP-3 on a low-tech tank?
thanks again everyone!