I think that aside from some possible software tweaks (the 990's software bears some significant differences from the P-965's software), the two use the same hardware at least. Several people have reported cases where the 990 tried to set surrounds to large instead of small. One thing to keep in mind - both units use a subwoofer test tone that is full-range. Because of this, Outlaw recommends that users turn on the crossover in their sub (on the LFM-1, this means flipping the X-OVER switch from "BYPASS" to "ACTIVE") and setting it to its highest position (around 180Hz on the LFM-1) before running auto-calibration or before calibrating the sub with the built-in test tone. This may help the P-965's auto-calibration give you more accurate results.