Gene, welcome. There may be a problem with the VP100, but one point that isn't clear from your description is the mode you used for playing 5.1 DVDs. Playing a 5.1 DVD on a 5.1 setup doesn't require any special processing, such as DPLII, just regular Dolby Digital.

On the setting-up, probably you should have the 2500 skip the speaker size and crossover settings and manually set all small and 80Hz(also try 100Hz), as you apparently already tried.

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Enjoy the music, not the equipment.