Based on specs, the 990 lacks XM radio and Audyssey EQ. On the surround mode side, they two are equally matched, with all of the same core processing modes. The 990 has Dolby Headphone (which the 3806 lacks), while the 3806 has an assortment of "DSP modes" (Jazz, Stadium, ...) that the 990 lacks. The 3806's HDMI inputs are v1.1 compliant, which is the only feature that I'd say might make a difference to you. The others here who have heard both seem to be giving the nod on sound quality to the 990, and I don't doubt them.