You don't understand Bi-Amping at all the 805 is the same amplification for the highs and the lows, true bi-amping is you run a different amplifier for your highs and a different amplifier for your lows, so if you feel the need that you love the high but the lows you don't like so much then you change your bottom end just say you have a Bryston 4b to do the Low and then you love the high on a Linn amplifier so you combine the Two to get a very sweet sound that you prefer, that way they give you a option on your speakers.
I do believe you can hear a difference on your 805 but it's only a small change you are getting.
I used to bi-amp on my old RB1080 Rotel but I sold them and bought a Musical Fidelity M6i and there no point in Bi-amping this amplifier am not even bi-wiring, my cable are CV-8 Audioquest 72v DBS and love the sound.
but If I was you Just Bi-amp if it make you happy don't let people tell you different also most of the time I watch 5.1 so the other 2ch are not even getting used you might of well bi-amp and use the 2 extra channels all the time