Hm. Assuming the dealer is right on all counts in how it works, you will effectively be getting low-pass only still (again, assuming mains are always full-range). No high pass filter for mains. *Now, really, do what pleases you, but not giving the mains a high-pass while engaging sub is generally not recommended. (For Kolida too, oh nice rig btw) the phase and amplitude issues I mentioned will generally expose themselves as muddy and unclear lower registers. You should understand that 2.1 audiophiles that use towers rather than bookshelves seem to be crossing-over as low as the hi-20's to as high as 40-ish hz. At least, that's what I've perceived. (The few people that use my speakers in 2.1 rig seem to like at it around 28hz). Again, if it sounds good to you, who is to argue. I've tried low-pass only already, and while I do enjoy some of the added things that come more into the foreground (I think jazz walking bass for ex), things are just too muddy, unclear, and inaccurate for me. Waiting on either a BM unit and/or nice Audyssey system. Speaking of:
I knew that the 805 is supposed to be quite a nice piece (60 amps, MultiEQ right?). I've set up a few Onkyo's already in my extremely limited audio experiences, and the ones I've seen do not have continuously variable x-over, nor "flick-of-a-switch" x-over presets. Even in my own pre/pro, even if the limited settings of 40/60/80 etc were good enough, it would be a downright pain to turn the tv on each time, check the OSD, change x-over setting for every time I went back and forth from HT and 2-ch. Well, this was perhaps the half-baked reasoning behind my statement, "Easiest and most expensive way...".
As far as frequency response correction, j_garcia is right, the Audyssey should do a better job on its own that even an SMS-1. I've never set one up, so I have nothing else to offer, and I do not know how truly flexible they might or might not be. It will work a larger area as well, not just for one perfect sweet spot. Time domain correction they call it; identifies and corrects overhang that would not necessarily show up on a simple level meter, if what I understand is correct.
A lot of blabber, but not much substitution for trying for yourself!