500 and the mini dsp. Here's why. You want the most sub you can afford. I have the 350, but am very, very lucky to have a lot of room gain to get me down to 20 Hz flat. I wish I had sub 20Hz bass for movies.

Even though the 500 is dsp controlled (actually the 350 has some dsp as well), it cannot be adjusted for your room. It is there to get the best output from the sub before the room boost some frequencies and sucks out others.

The Minidsp will allow you to adjust for the peculiarities of your room. In my case I had a HUGE wide (big ass?) 15db peak at 54 Hz that definitely effected the sound in my room. I used REW to measure the room and fed the filters suggested by it into a Behringer feedback destroyer (not quite as good as the minidsp) to considerably improve my sound.
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Fred

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Blujays1: Spending Fred's money one bottle at a time, no two... Oh crap!