The Minstral and the dB500 model almost identical regardless of which set of parameters you use. I'd say the minstral T/S numbers are good since using DVC does change things slightly. Both drivers work well in an vertical mount configuration. %SAG=24849/(Xmax*Fs^2) If it is the same as the db-500, Xmax is 20mm. I don't have Xmech, but I've never bottomed mine out. That puts your percent SAG at ~2%.
I've never experienced any magnetic shielding problems or issues with the screen shaking. I suppose that will depend on your exact set. I built another "behind the TV corner sub" for a buddy and his RPTV has no issues either. You might be a little more concerned if you have a CRT projection screen, but I don't remember if you said what type you have. I used a Fi driver in his and it turned out fabulous as well. check it out.
http://www.hometheatershack.com/foru...-im-again.html
Finally, your amp....Do you have room for a pro-amp. You can buy a Behringer A500 that will give you 240W into two 4 ohm channels for 200$. I think that would be a perfect match to the DVC Minstral. In fact, If I had known about the Minstral driver, I probably would have done that instead of a db-500 and a buttkicker amp. If you need to spend a little less, a Pyramid PA600X for $150 will give you 150W into two 4ohm channels. Otherwise, I wouldn't try to connect a DVC in parallel to a 4ohm plate amp and series would limit the power output.