I was given a pair of Polk LSi9, receiver options include 6700h I am being told that bi-amp the lsi9 with the height channels will be best. If no bi-amp, needed, am being told to save money and get the 4700 could work. is the 6700h better for the Lsi9? I would like to end with either a 7.1.2 or 7.1.4. Thank you in advance for the help.