My advise is to go with 3600 between the two. Newer product and same calibration software. Will do 11 channels.
I would suggest a quality external amplifier for your LSi speakers. They are top of the line polk audios, but not easy to drive like their RTi/RTiA line. The power deficiency is more noticeable when playing music than movies. The receivers ratings provided are usually 1 or 2 channel driven (sometimes even at 4 ohms). You have the subwoofers doing the heavy lifting but with LSi line I would suggest at least a 2 or 3 channel amplifier to drive the front two/three. The reason I stayed with RTi line for home theater is because they are bright and easy to drive with less power, although I have external amplifier powering the front 3, I can get by without it if I were listening at moderate volume levels.
Whichever receiver you decide to go with, be careful with the volume knob till you have an external amplifier added.
living room: 60" 4k TV | XBox one S | Apple TV 4k | Fire tv stick 4k | Sony BDP 6500| Yamaha rx-v7810 | Polk Audio 65RT 7 channels | Dayton Audio sub-120 | incomplete theater: 166" 2.40:1 AT screen | Benq w1070 | Sony SACD player | Sony BDP 6500 | Yamaha rx-v667 | Adcom 5600->Polk audio RTi8 | CSi5 | FXiA3 | RTi4 | inuke nu1000dsp -> 2 VBSS subwoofer |Office: Denon 1930CI SACD player | Yamaha rx-a730 | Polk RTi4