Thanks. A few things have changed, mainly the addition of diffuser drapes on the front wall (closed for music; diffusion really helps soundstage and imaging and getting rid of that huge relective screen area) and the movement of the Sunfire subs to an approx 1/5th position along the front wall, facing the lp. I'll be reporting back on what I end up with position-wise, using the put-subs-in-lp-position approach.. The Sunfires subs are gonna be replaced, but since a possible great deal on nearly new VMPS Largers fell through I am not ready yet with that replacement. The SMS-1 is clearly making the current subs work a lot better in the meantime.

Yeah, your sweep shot makes me think the rolloff after 160hz is no big deal. Thanks.