Sorry in advance if this is a stupid question...
I just purchased a Acoustech H-100 sub, which is not magnetically shielded. If I place it next to my Boston VR3 tower, which is shielded, will the speakers interfere with each other magnetically? (one is shielded, one is not)

Should be no audible effect. The main field from the unshielded speaker is a static field from the permanent magnet. The same is true for the unshielded speakers. The small changing field induced by current flowing in the unshielded subwoofer speaker will not produce changes in the voice coil of the unshielded speaker. Putting it next to a CRT TV or a monitor however will likely cause large picture distortions because of the static field .

..Doyle

good response, thank you! Should a foot or so be enough distance from my CRT?

Slide it up until you can see the picture change and you will know if you have a problem. If you see no picture change then you should be good to go.

..Doyle

Should a foot or so be enough distance from my CRT?

From experience, I would say that that's marginal. You might have to move it further. However, try it first; if you think it's fine, then no need to change anything.