I have my 641 sub and casing placed on the floor beneath the table. They are placed more than 2 feet apart. I don't think there is much to worry about the vibration NV30....unless you place your sub like around 2 feet or less(ttoo close aint good for the hard drives) .... plus there is some rubber pad below your sub, that should help to slow down the vibration from reaching your case and before it even reaches the case, vibration will be minimum. IMO If you are too worried get rubber pads for your casing.
Rusty, till this date what i know is that there are two types of subwoofer, directional and no-directional...i can't explain in detail because im too good at this point but i can advise in how to place them.
Non-directional sub - Such a sub do not need to be postioned in any particular relation to the satellites, but in order for the sub to produce maximum bass effieciency, it would be better to place the sub close to the wall or the corner of your room.
Directional sub - a correct placement in particular relation to the satellites must be taken note to achieve maximum bass efficient, ie. by placing the sub 90 degrees to the two front satellites.